diff --git a/Controller/IntrospectionController.php b/Controller/IntrospectionController.php
index 2c26f681..3e6a1635 100644
--- a/Controller/IntrospectionController.php
+++ b/Controller/IntrospectionController.php
@@ -13,13 +13,19 @@
 
 namespace FOS\OAuthServerBundle\Controller;
 
+use FOS\OAuthServerBundle\Form\Model\Introspect;
+use FOS\OAuthServerBundle\Form\Type\IntrospectionFormType;
 use FOS\OAuthServerBundle\Model\AccessTokenInterface;
 use FOS\OAuthServerBundle\Model\RefreshTokenInterface;
 use FOS\OAuthServerBundle\Model\TokenInterface;
 use FOS\OAuthServerBundle\Model\TokenManagerInterface;
+use FOS\OAuthServerBundle\Security\Authentication\Token\OAuthToken;
+use Symfony\Component\Form\FormFactory;
 use Symfony\Component\HttpFoundation\JsonResponse;
 use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpKernel\Exception\BadRequestHttpException;
 use Symfony\Component\Security\Core\Authentication\Token\Storage\TokenStorageInterface;
+use Symfony\Component\Security\Core\Exception\AccessDeniedException;
 
 class IntrospectionController
 {
@@ -38,21 +44,47 @@ class IntrospectionController
      */
     private $refreshTokenManager;
 
+    /**
+     * @var FormFactory
+     */
+    private $formFactory;
+
+    /**
+     * @var array
+     */
+    private $allowedIntrospectionClients;
+
     public function __construct(
         TokenStorageInterface $tokenStorage,
         TokenManagerInterface $accessTokenManager,
-        TokenManagerInterface $refreshTokenManager
+        TokenManagerInterface $refreshTokenManager,
+        FormFactory $formFactory,
+        array $allowedIntrospectionClients
     ) {
         $this->tokenStorage = $tokenStorage;
         $this->accessTokenManager = $accessTokenManager;
         $this->refreshTokenManager = $refreshTokenManager;
+        $this->formFactory = $formFactory;
+        $this->allowedIntrospectionClients = $allowedIntrospectionClients;
     }
 
     public function introspectAction(Request $request): JsonResponse
     {
-        // $clientToken = $this->tokenStorage->getToken(); → use in security
+        $clientToken = $this->tokenStorage->getToken(); // → use in security
+
+        if (!$clientToken instanceof OAuthToken) {
+            throw new AccessDeniedException('The introspect endpoint must be behind a secure firewall.');
+        }
 
-        // TODO security for this endpoint. Probably in the README documentation
+        $callerToken = $this->accessTokenManager->findTokenByToken($clientToken->getToken());
+
+        if (!$callerToken) {
+            throw new AccessDeniedException('The access token must have a valid token.');
+        }
+
+        if (!in_array($callerToken->getClientId(), $this->allowedIntrospectionClients)) {
+            throw new AccessDeniedException('This access token is not autorised to do introspection.');
+        }
 
         $token = $this->getToken($request);
 
@@ -79,8 +111,9 @@ public function introspectAction(Request $request): JsonResponse
      */
     private function getToken(Request $request)
     {
-        $tokenTypeHint = $request->request->get('token_type_hint'); // TODO move in a form type ? can be `access_token`, `refresh_token` See https://tools.ietf.org/html/rfc7009#section-4.1.2
-        $tokenString = $request->request->get('token'); // TODO move in a form type ?
+        $formData = $this->processIntrospectionForm($request);
+        $tokenString = $formData->token;
+        $tokenTypeHint = $formData->token_type_hint;
 
         $tokenManagerList = [];
         if (!$tokenTypeHint || 'access_token' === $tokenTypeHint) {
@@ -125,4 +158,21 @@ private function getUsername(TokenInterface $token)
 
         return $user->getUserName();
     }
+
+    private function processIntrospectionForm(Request $request): Introspect
+    {
+        $formData = new Introspect();
+        $form = $this->formFactory->create(IntrospectionFormType::class, $formData);
+        $form->handleRequest($request);
+
+        if (!$form->isSubmitted() || !$form->isValid()) {
+            $errors = $form->getErrors();
+            if (count($errors) > 0) {
+                throw new BadRequestHttpException((string) $errors);
+            } else {
+                throw new BadRequestHttpException('Introspection endpoint needs to have at least a "token" form parameter');
+            }
+        }
+        return $form->getData();
+    }
 }
diff --git a/DependencyInjection/Configuration.php b/DependencyInjection/Configuration.php
index 571fcafd..d2500fea 100644
--- a/DependencyInjection/Configuration.php
+++ b/DependencyInjection/Configuration.php
@@ -82,6 +82,7 @@ public function getConfigTreeBuilder()
         $this->addAuthorizeSection($rootNode);
         $this->addServiceSection($rootNode);
         $this->addTemplateSection($rootNode);
+        $this->addIntrospectionSection($rootNode);
 
         return $treeBuilder;
     }
@@ -151,4 +152,24 @@ private function addTemplateSection(ArrayNodeDefinition $node)
             ->end()
         ;
     }
+
+    private function addIntrospectionSection(ArrayNodeDefinition $node)
+    {
+        $node
+            ->addDefaultsIfNotSet()
+            ->children()
+                ->arrayNode('introspection')
+                    ->addDefaultsIfNotSet()
+                        ->children()
+                            ->arrayNode('allowed_clients')
+                                ->useAttributeAsKey('key')
+                                ->treatNullLike([])
+                                ->prototype('variable')->end()
+                            ->end()
+                        ->end()
+                    ->end()
+                ->end()
+            ->end()
+        ;
+    }
 }
diff --git a/DependencyInjection/FOSOAuthServerExtension.php b/DependencyInjection/FOSOAuthServerExtension.php
index 1a1fc008..8b84433a 100644
--- a/DependencyInjection/FOSOAuthServerExtension.php
+++ b/DependencyInjection/FOSOAuthServerExtension.php
@@ -102,7 +102,7 @@ public function load(array $configs, ContainerBuilder $container)
             $authorizeFormDefinition->setFactory([new Reference('form.factory'), 'createNamed']);
         }
 
-        $this->loadIntrospection($loader);
+        $this->loadIntrospection($config, $container, $loader);
     }
 
     /**
@@ -144,9 +144,12 @@ protected function remapParametersNamespaces(array $config, ContainerBuilder $co
         }
     }
 
-    protected function loadIntrospection(XmlFileLoader $loader)
+    protected function loadIntrospection(array $config, ContainerBuilder $container, XmlFileLoader $loader)
     {
         $loader->load('introspection.xml');
+
+        $allowedClients = $config['introspection']['allowed_clients'];
+        $container->setParameter('fos_oauth_server.introspection.allowed_clients', $allowedClients);
     }
 
     protected function loadAuthorize(array $config, ContainerBuilder $container, XmlFileLoader $loader)
diff --git a/Form/Model/Introspect.php b/Form/Model/Introspect.php
new file mode 100644
index 00000000..b419ed6a
--- /dev/null
+++ b/Form/Model/Introspect.php
@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the FOSOAuthServerBundle package.
+ *
+ * (c) FriendsOfSymfony <http://friendsofsymfony.github.com/>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FOS\OAuthServerBundle\Form\Model;
+
+use Symfony\Component\Validator\Constraints as Assert;
+
+class Introspect
+{
+    /**
+     * @var string
+     * @Assert\NotBlank()
+     */
+    public $token;
+
+    /**
+     * @var string
+     */
+    public $token_type_hint;
+}
diff --git a/Form/Type/IntrospectionFormType.php b/Form/Type/IntrospectionFormType.php
new file mode 100644
index 00000000..b169cf5a
--- /dev/null
+++ b/Form/Type/IntrospectionFormType.php
@@ -0,0 +1,54 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of the FOSOAuthServerBundle package.
+ *
+ * (c) FriendsOfSymfony <http://friendsofsymfony.github.com/>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace FOS\OAuthServerBundle\Form\Type;
+
+use FOS\OAuthServerBundle\Form\Model\Introspect;
+use Symfony\Component\Form\AbstractType;
+use Symfony\Component\Form\Extension\Core\Type\ChoiceType;
+use Symfony\Component\Form\Extension\Core\Type\HiddenType;
+use Symfony\Component\Form\FormBuilderInterface;
+use Symfony\Component\OptionsResolver\OptionsResolver;
+
+class IntrospectionFormType extends AbstractType
+{
+    public function buildForm(FormBuilderInterface $builder, array $options)
+    {
+        $builder->add('token', HiddenType::class);
+        $builder->add('token_type_hint', ChoiceType::class, [ // can be `access_token`, `refresh_token` See https://tools.ietf.org/html/rfc7009#section-4.1.2
+            'choices' => [
+                'access_token' => 'access_token',
+                'refresh_token' => 'refresh_token',
+            ]
+        ]);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function configureOptions(OptionsResolver $resolver)
+    {
+        $resolver->setDefaults([
+            'data_class' => Introspect::class,
+            'csrf_protection' => false,
+        ]);
+    }
+
+    /**
+     * @return string
+     */
+    public function getBlockPrefix()
+    {
+        return '';
+    }
+}
diff --git a/Resources/config/introspection.xml b/Resources/config/introspection.xml
index 7bc972b1..da9d1cd6 100644
--- a/Resources/config/introspection.xml
+++ b/Resources/config/introspection.xml
@@ -9,6 +9,8 @@
             <argument type="service" id="security.token_storage" />
             <argument type="service" id="fos_oauth_server.access_token_manager" />
             <argument type="service" id="fos_oauth_server.refresh_token_manager" />
+            <argument type="service" id="form.factory" />
+            <argument>%fos_oauth_server.introspection.allowed_clients%</argument>
         </service>
     </services>