diff --git a/apistar/__init__.py b/apistar/__init__.py
index b9237a96..8fca20b2 100644
--- a/apistar/__init__.py
+++ b/apistar/__init__.py
@@ -1,3 +1,4 @@
+# flake8: noqa
 """
               _    ____ ___   ____  _
  __/\__      / \  |  _ \_ _| / ___|| |_ __ _ _ __    __/\__
diff --git a/apistar/document.py b/apistar/document.py
index ae26bf6f..c3765ac2 100644
--- a/apistar/document.py
+++ b/apistar/document.py
@@ -9,11 +9,11 @@
 
 class Document:
     def __init__(self,
-                 content: typing.Sequence[typing.Union['Section', 'Link']]=None,
-                 url: str='',
-                 title: str='',
-                 description: str='',
-                 version: str=''):
+                 content: typing.Sequence[typing.Union['Section', 'Link']] = None,
+                 url: str = '',
+                 title: str = '',
+                 description: str = '',
+                 version: str = ''):
         content = [] if (content is None) else list(content)
 
         # Ensure all names within a document are unique.
@@ -55,9 +55,9 @@ def walk_links(self):
 class Section:
     def __init__(self,
                  name: str,
-                 content: typing.Sequence[typing.Union['Section', 'Link']]=None,
-                 title: str='',
-                 description: str=''):
+                 content: typing.Sequence[typing.Union['Section', 'Link']] = None,
+                 title: str = '',
+                 description: str = ''):
         content = [] if (content is None) else list(content)
 
         # Ensure all names within a section are unique.
@@ -104,13 +104,13 @@ class Link:
     def __init__(self,
                  url: str,
                  method: str,
-                 handler: typing.Callable=None,
-                 name: str='',
-                 encoding: str='',
-                 response: 'Response'=None,
-                 title: str='',
-                 description: str='',
-                 fields: typing.Sequence['Field']=None):
+                 handler: typing.Callable = None,
+                 name: str = '',
+                 encoding: str = '',
+                 response: 'Response' = None,
+                 title: str = '',
+                 description: str = '',
+                 fields: typing.Sequence['Field'] = None):
         method = method.upper()
         fields = [] if (fields is None) else list(fields)
 
@@ -173,11 +173,11 @@ class Field:
     def __init__(self,
                  name: str,
                  location: str,
-                 title: str='',
-                 description: str='',
-                 required: bool=None,
-                 schema: Validator=None,
-                 example: typing.Any=None):
+                 title: str = '',
+                 description: str = '',
+                 required: bool = None,
+                 schema: Validator = None,
+                 example: typing.Any = None):
         assert location in ('path', 'query', 'body', 'cookie', 'header', 'formData')
         if required is None:
             required = True if location in ('path', 'body') else False
@@ -194,7 +194,7 @@ def __init__(self,
 
 
 class Response:
-    def __init__(self, encoding: str, status_code: int=200, schema: Validator=None):
+    def __init__(self, encoding: str, status_code: int = 200, schema: Validator = None):
         self.encoding = encoding
         self.status_code = status_code
         self.schema = schema
diff --git a/apistar/schemas/openapi.py b/apistar/schemas/openapi.py
index 6dda2173..f3a57935 100644
--- a/apistar/schemas/openapi.py
+++ b/apistar/schemas/openapi.py
@@ -5,6 +5,7 @@
 from apistar.compat import dict_type
 from apistar.document import Document, Field, Link, Section
 from apistar.schemas.jsonschema import JSON_SCHEMA, JSONSchema
+from apistar.validators import Validator
 
 SCHEMA_REF = validators.Object(
     properties={'$ref': validators.String(pattern='^#/components/schemas/')}
@@ -15,6 +16,9 @@
 RESPONSE_REF = validators.Object(
     properties={'$ref': validators.String(pattern='^#/components/responses/')}
 )
+PARAMETERS_REF = validators.Object(
+    properties={'$ref': validators.String(pattern='^#/components/parameters/')}
+)
 
 OPEN_API = validators.Object(
     def_name='OpenAPI',
@@ -116,7 +120,7 @@
                 ('patch', validators.Ref('Operation')),
                 ('trace', validators.Ref('Operation')),
                 ('servers', validators.Array(items=validators.Ref('Server'))),
-                ('parameters', validators.Array(items=validators.Ref('Parameter'))),  # TODO: | ReferenceObject
+                ('parameters', validators.Array(items=validators.Ref('Parameter') | PARAMETERS_REF)),
             ],
             pattern_properties={
                 '^x-': validators.Any(),
@@ -130,7 +134,7 @@
                 ('description', validators.String(format='textarea')),
                 ('externalDocs', validators.Ref('ExternalDocumentation')),
                 ('operationId', validators.String()),
-                ('parameters', validators.Array(items=validators.Ref('Parameter'))),  # TODO: | ReferenceObject
+                ('parameters', validators.Array(items=validators.Ref('Parameter') | PARAMETERS_REF)),
                 ('requestBody', REQUESTBODY_REF | validators.Ref('RequestBody')),  # TODO: RequestBody | ReferenceObject
                 ('responses', validators.Ref('Responses')),
                 # TODO: 'callbacks'
@@ -314,7 +318,8 @@ def load(self, data):
         version = lookup(data, ['info', 'version'])
         base_url = lookup(data, ['servers', 0, 'url'])
         schema_definitions = self.get_schema_definitions(data)
-        content = self.get_content(data, base_url, schema_definitions)
+        parameter_definitions = self.get_parameter_definitions(data, schema_definitions)
+        content = self.get_content(data, base_url, schema_definitions, parameter_definitions)
 
         return Document(title=title, description=description, version=version, url=base_url, content=content)
 
@@ -326,7 +331,26 @@ def get_schema_definitions(self, data):
             definitions[key].def_name = key
         return definitions
 
-    def get_content(self, data, base_url, schema_definitions):
+    def get_validator(self, schema, schema_definitions):
+        if schema is None or isinstance(schema, Validator):
+            return schema
+
+        if '$ref' in schema:
+            ref = schema['$ref'][len('#/components/schemas/'):]
+            return schema_definitions.get(ref)
+        else:
+            return JSONSchema().decode_from_data_structure(schema)
+
+    def get_parameter_definitions(self, data, schema_definitions):
+        definitions = {}
+        parameters = lookup(data, ['components', 'parameters'], {})
+        for key, value in parameters.items():
+            value["schema"] = self.get_validator(value.get("schema"), schema_definitions)
+            value["schema"].def_name = key
+            definitions[key] = value
+        return definitions
+
+    def get_content(self, data, base_url, schema_definitions, parameter_definitions):
         """
         Return all the links in the document, layed out by tag and operationId.
         """
@@ -340,7 +364,8 @@ def get_content(self, data, base_url, schema_definitions):
             }
             for operation, operation_info in operations.items():
                 tag = lookup(operation_info, ['tags', 0])
-                link = self.get_link(base_url, path, path_info, operation, operation_info, schema_definitions)
+                link = self.get_link(
+                    base_url, path, path_info, operation, operation_info, schema_definitions, parameter_definitions)
                 if link is None:
                     continue
 
@@ -357,7 +382,7 @@ def get_content(self, data, base_url, schema_definitions):
         ]
         return links + sections
 
-    def get_link(self, base_url, path, path_info, operation, operation_info, schema_definitions):
+    def get_link(self, base_url, path, path_info, operation, operation_info, schema_definitions, parameter_definitions):
         """
         Return a single link in the document.
         """
@@ -379,7 +404,7 @@ def get_link(self, base_url, path, path_info, operation, operation_info, schema_
         parameters += operation_info.get('parameters', [])
 
         fields = [
-            self.get_field(parameter, schema_definitions)
+            self.get_field(parameter, schema_definitions, parameter_definitions)
             for parameter in parameters
         ]
 
@@ -409,24 +434,21 @@ def get_link(self, base_url, path, path_info, operation, operation_info, schema_
             encoding=encoding
         )
 
-    def get_field(self, parameter, schema_definitions):
+    def get_field(self, parameter, schema_definitions, parameter_definitions):
         """
         Return a single field in a link.
         """
+        if '$ref' in parameter:
+            ref = parameter['$ref'][len('#/components/parameters/'):]
+            parameter = parameter_definitions.get(ref)
+
         name = parameter.get('name')
         location = parameter.get('in')
         description = parameter.get('description')
         required = parameter.get('required', False)
-        schema = parameter.get('schema')
+        schema = self.get_validator(parameter.get('schema'), schema_definitions)
         example = parameter.get('example')
 
-        if schema is not None:
-            if '$ref' in schema:
-                ref = schema['$ref'][len('#/components/schemas/'):]
-                schema = schema_definitions.get(ref)
-            else:
-                schema = JSONSchema().decode_from_data_structure(schema)
-
         return Field(
             name=name,
             location=location,
diff --git a/apistar/tokenize/tokens.py b/apistar/tokenize/tokens.py
index e2370aa8..47f1e9cb 100644
--- a/apistar/tokenize/tokens.py
+++ b/apistar/tokenize/tokens.py
@@ -9,7 +9,7 @@ def __init__(self, value, start_index: int, end_index: int, content=None):
         self._content = content
 
     def get_value(self):
-        raise NotImplemented()  # pragma: nocover
+        raise NotImplementedError()  # pragma: nocover
 
     @property
     def start(self):
diff --git a/testcases/openapi/parameters-example.yaml b/testcases/openapi/parameters-example.yaml
new file mode 100644
index 00000000..ce14d3e2
--- /dev/null
+++ b/testcases/openapi/parameters-example.yaml
@@ -0,0 +1,52 @@
+openapi: 3.0.2
+info: 
+  title: Parameters Example
+  version: 1.0.0
+paths:
+  /parameters:
+    get:
+      operationId: getParameters
+      parameters:
+        - $ref: '#/components/parameters/Simple'
+        - $ref: '#/components/parameters/SimpleSchemaReference'
+        - name: inline
+          in: query
+          description: 'Query parameter defined inline'
+          required: false
+          schema:
+            type: string
+        - name: inline_schema_reference
+          in: query
+          description: 'Query parameter defined inline but with referenced schema'
+          required: false
+          schema:
+            $ref: '#/components/schemas/SchemaReference'
+      responses:
+        '200':
+          description: success
+          content:
+            application/json:
+              schema:
+                type: object
+                properties:
+                  status:
+                    type: string
+components:
+  parameters:
+    Simple:
+      name: simple
+      in: query
+      description: 'Simple query parameters defined as component'
+      required: false
+      schema:
+        type: string
+    SimpleSchemaReference:
+      name: simple_schema_reference
+      in: query
+      description: 'Simple query parameters defined as component with schema referenced'
+      required: false
+      schema:
+        $ref: '#/components/schemas/SchemaReference'
+  schemas: 
+    SchemaReference:
+      type: string
\ No newline at end of file
diff --git a/tests/client/test_client.py b/tests/client/test_client.py
index cc7dce7d..05cf6d94 100644
--- a/tests/client/test_client.py
+++ b/tests/client/test_client.py
@@ -10,7 +10,8 @@
 
 
 @app.route('/path-param/{value}')
-def path_param(request, value):
+def path_param(request):
+    value = request.path_params['value']
     return JSONResponse({'value': value})
 
 
diff --git a/tests/schemas/test_openapi.py b/tests/schemas/test_openapi.py
index a48a39ba..ac2a1b54 100644
--- a/tests/schemas/test_openapi.py
+++ b/tests/schemas/test_openapi.py
@@ -9,6 +9,7 @@
     # 'testcases/openapi/callback-example.yaml',
     # 'testcases/openapi/link-example.yaml',
     'testcases/openapi/petstore-expanded.yaml',
+    'testcases/openapi/parameters-example.yaml',
     'testcases/openapi/petstore.yaml',
     'testcases/openapi/uspto.yaml',
 ]