diff --git a/src/Symfony/Component/Form/Event/ChildDataEvent.php b/src/Symfony/Component/Form/Event/ChildDataEvent.php
new file mode 100644
index 0000000000000..651f7b62befaa
--- /dev/null
+++ b/src/Symfony/Component/Form/Event/ChildDataEvent.php
@@ -0,0 +1,48 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Form\Event;
+
+use Symfony\Component\Form\FormInterface;
+
+class ChildDataEvent extends DataEvent
+{
+    private $name;
+
+    /**
+     * Constructs an event.
+     *
+     * @param FormInterface $form The associated form
+     * @param string        $name The name of the field that was just set
+     * @param mixed         $data The data of the field that was just set
+     */
+    public function __construct(FormInterface $form, $name, $data)
+    {
+        $this->name = $name;
+        parent::__construct($form, $data);
+    }
+
+    /**
+     * Gets the data of the field that was just set
+     */
+    public function getData()
+    {
+        return parent::getData();
+    }
+
+    /**
+     * Gets the name of the field that was updated
+     */
+    public function getName()
+    {
+        return $this->name;
+    }
+}
diff --git a/src/Symfony/Component/Form/Form.php b/src/Symfony/Component/Form/Form.php
index 0e68b88c01edf..f886fff7043e3 100644
--- a/src/Symfony/Component/Form/Form.php
+++ b/src/Symfony/Component/Form/Form.php
@@ -13,6 +13,7 @@
 
 use Symfony\Component\Form\Event\DataEvent;
 use Symfony\Component\Form\Event\FilterDataEvent;
+use Symfony\Component\Form\Event\ChildDataEvent;
 use Symfony\Component\Form\Exception\FormException;
 use Symfony\Component\Form\Exception\AlreadyBoundException;
 use Symfony\Component\Form\Exception\UnexpectedTypeException;
@@ -506,13 +507,21 @@ public function bind($clientData)
                 }
             }
 
-            foreach ($clientData as $name => $value) {
-                if ($this->has($name)) {
-                    $this->children[$name]->bind($value);
-                } else {
-                    $extraData[$name] = $value;
+            $extraData = $clientData;
+            do {
+                $lastChildren = $this->children;
+                foreach ($extraData as $name => $value) {
+                    if ($this->has($name)) {
+                        $this->children[$name]->bind($value);
+                        unset($extraData[$name]);
+
+                        // every time we bind a child, we dispatch an event to allow
+                        // listeners to add or remove field based on the result value
+                        $event = new ChildDataEvent($this, $name, $this->children[$name]->getData());
+                        $this->dispatcher->dispatch(FormEvents::BIND_CHILD, $event);
+                    }
                 }
-            }
+            } while(count($extraData) && $lastChildren !== $this->children);
 
             // If we have a data mapper, use old client data and merge
             // data from the children into it later
diff --git a/src/Symfony/Component/Form/FormEvents.php b/src/Symfony/Component/Form/FormEvents.php
index a97337ec5a187..a30f66ab75623 100644
--- a/src/Symfony/Component/Form/FormEvents.php
+++ b/src/Symfony/Component/Form/FormEvents.php
@@ -26,6 +26,8 @@ final class FormEvents
 
     const BIND_CLIENT_DATA = 'form.bind_client_data';
 
+    const BIND_CHILD = 'form.bind_child';
+
     const BIND_NORM_DATA = 'form.bind_norm_data';
 
     const SET_DATA = 'form.set_data';
diff --git a/src/Symfony/Component/Form/Tests/FormTest.php b/src/Symfony/Component/Form/Tests/FormTest.php
index d6784f4e52393..e47e15318f430 100644
--- a/src/Symfony/Component/Form/Tests/FormTest.php
+++ b/src/Symfony/Component/Form/Tests/FormTest.php
@@ -22,6 +22,8 @@
 use Symfony\Component\EventDispatcher\EventDispatcherInterface;
 use Symfony\Component\Form\Tests\Fixtures\FixedDataTransformer;
 use Symfony\Component\Form\Tests\Fixtures\FixedFilterListener;
+use Symfony\Component\Form\Event\ChildDataEvent;
+use Symfony\Component\Form\FormEvents;
 
 class FormTest extends \PHPUnit_Framework_TestCase
 {
@@ -1303,6 +1305,78 @@ public function testGetValidatorsReturnsValidators()
 
         $this->assertEquals(array($validator), $form->getValidators());
     }
+    
+    public function testBindChild()
+    {
+        $field1builder = $this->getBuilder('field1');
+        $field2builder = $this->getBuilder('field2');
+        
+        $builder = $this->getBuilder('form', new EventDispatcher())
+            ->addEventListener(FormEvents::BIND_CHILD, function(ChildDataEvent $e) use ($field2builder) {
+                if ($e->getName() == 'field1') {
+                    if ($e->getData() == 'a') {
+                        $e->getForm()->add($field2builder->getForm());
+                    } else {
+                        $e->getForm()->remove('field2');
+                    }
+                }
+            });
+        $form = $builder->getForm();
+        $form->add($field1builder->getForm());
+
+        $form->bind(array('field1'=>'a', 'field2'=>'b'));
+        $this->assertTrue($form->has('field2'));
+        $this->assertEmpty($form->getExtraData());
+
+        $form = $builder->getForm();
+        $form->add($field1builder->getForm());
+        $form->add($field2builder->getForm());
+
+        $form->bind(array('field1'=>'b', 'field2'=>'a'));
+        $this->assertFalse($form->has('field2'));
+        $this->assertEquals(array('field2'=>'a'), $form->getExtraData());
+    }
+
+    public function testBindChildDoesntResultInEndlessLoop()
+    {
+        $field1builder = $this->getBuilder('field1');
+
+        $builder = $this->getBuilder('form');
+
+        $form = $builder->getForm();
+        $form->add($field1builder->getForm());
+
+        $form->bind(array('field1'=>'a', 'field2'=>'b'));
+    }
+
+    public function testBindChildKeepsLoopingUntilNoFieldsAreAdded()
+    {
+        $transformer = $this->getDataTransformer();
+        $transformer->expects($this->exactly(3))->method('reverseTransform')->will($this->onConsecutiveCalls(array('abound', 'bbound', 'cbound')));
+
+        $field2builder = $this->getBuilder('field2')->appendClientTransformer($transformer);
+        $field3builder = $this->getBuilder('field3')->appendClientTransformer($transformer);
+
+        $builder = $this->getBuilder('form', new EventDispatcher())
+            ->addEventListener(FormEvents::BIND_CHILD, function(ChildDataEvent $e) use ($field2builder, $field3builder) {
+                if ($e->getName() == 'field1') {
+                    $e->getForm()->add($field2builder->getForm());
+                } elseif ($e->getName() == 'field2') {
+                    $e->getForm()->add($field3builder->getForm());
+                }
+            });
+
+        $form = $builder->getForm();
+
+        $form->add($this->getBuilder('field1')->appendClientTransformer($transformer)->getForm());
+
+        $form->bind(array('field1'=>'a', 'field2'=>'b', 'field3'=>'c', 'field4'=>'d'));
+        
+        // issue #3770
+        //$this->assertEquals(array('field1'=>'abound', 'field2'=>'bbound', 'field3'=>'cbound', 'field4'=>'d'), $form->getData());
+        $this->assertEquals(array('field1'=>'a', 'field2'=>'b', 'field3'=>'c', 'field4'=>'d'), $form->getData());
+        $this->assertEquals(array('field4'=>'d'), $form->getExtraData());
+    }
 
     protected function getBuilder($name = 'name', EventDispatcherInterface $dispatcher = null)
     {