diff --git a/README.md b/README.md
index 8154a17..6b55cae 100644
--- a/README.md
+++ b/README.md
@@ -52,7 +52,7 @@ $names = Collection::init($employees)
     ->sortedByDescending(function ($value) {
         return $value['age'];
     })
-    ->mapValues(function ($value) {
+    ->map(function ($value) {
         return $value['name'];
     })
     ->toArray();
diff --git a/src/collections_me.c b/src/collections_me.c
index 49e128c..571eff4 100644
--- a/src/collections_me.c
+++ b/src/collections_me.c
@@ -168,11 +168,7 @@ const zend_function_entry collection_methods[] = {
     PHP_ME(Collection, last, predicate_arginfo, ZEND_ACC_PUBLIC)
     PHP_ME(Collection, lastIndexOf, element_arginfo, ZEND_ACC_PUBLIC)
     PHP_ME(Collection, map, transform_arginfo, ZEND_ACC_PUBLIC)
-    PHP_ME(Collection, mapKeys, transform_arginfo, ZEND_ACC_PUBLIC)
-    PHP_ME(Collection, mapKeysTo, destination_transform_arginfo, ZEND_ACC_PUBLIC)
     PHP_ME(Collection, mapTo, destination_transform_arginfo, ZEND_ACC_PUBLIC)
-    PHP_ME(Collection, mapValues, transform_arginfo, ZEND_ACC_PUBLIC)
-    PHP_ME(Collection, mapValuesTo, destination_transform_arginfo, ZEND_ACC_PUBLIC)
     PHP_ME(Collection, max, NULL, ZEND_ACC_PUBLIC)
     PHP_ME(Collection, maxBy, selector_arginfo, ZEND_ACC_PUBLIC)
     PHP_ME(Collection, maxWith, comparator_arginfo, ZEND_ACC_PUBLIC)
diff --git a/src/collections_methods.c b/src/collections_methods.c
index 7e7b150..00c7aff 100644
--- a/src/collections_methods.c
+++ b/src/collections_methods.c
@@ -1023,32 +1023,39 @@ PHP_METHOD(Collection, lastIndexOf)
 
 PHP_METHOD(Collection, map)
 {
-    
-}
-
-PHP_METHOD(Collection, mapKeys)
-{
-    
-}
-
-PHP_METHOD(Collection, mapKeysTo)
-{
-    
+    zend_fcall_info fci;
+    zend_fcall_info_cache fcc;
+    ZEND_PARSE_PARAMETERS_START(1, 1)
+        Z_PARAM_FUNC(fci, fcc)
+    ZEND_PARSE_PARAMETERS_END();
+    INIT_FCI(2);
+    zend_array* current = COLLECTION_FETCH_CURRENT();
+    ARRAY_NEW_EX(new_collection, current);
+    ZEND_HASH_FOREACH_BUCKET(current, Bucket* bucket)
+        CALLBACK_KEYVAL_INVOKE(params, bucket);
+        zend_hash_next_index_insert(new_collection, &retval);
+    ZEND_HASH_FOREACH_END();
+    RETVAL_NEW_COLLECTION(new_collection);
 }
 
 PHP_METHOD(Collection, mapTo)
 {
-    
-}
-
-PHP_METHOD(Collection, mapValues)
-{
-    
-}
-
-PHP_METHOD(Collection, mapValuesTo)
-{
-    
+    zend_fcall_info fci;
+    zend_fcall_info_cache fcc;
+    zval* dest;
+    ZEND_PARSE_PARAMETERS_START(2, 2)
+        Z_PARAM_OBJECT_OF_CLASS(dest, collections_collection_ce)
+        Z_PARAM_FUNC(fci, fcc)
+    ZEND_PARSE_PARAMETERS_END();
+    INIT_FCI(2);
+    zend_array* current = COLLECTION_FETCH_CURRENT();
+    zend_array* dest_arr = COLLECTION_FETCH(dest);
+    SEPARATE_COLLECTION(dest_arr, dest);
+    ZEND_HASH_FOREACH_BUCKET(current, Bucket* bucket)
+        CALLBACK_KEYVAL_INVOKE(params, bucket);
+        zend_hash_next_index_insert(dest_arr, &retval);
+    ZEND_HASH_FOREACH_END();
+    RETVAL_ZVAL(dest, 1, 0);
 }
 
 PHP_METHOD(Collection, max)
diff --git a/src/php_collections_me.h b/src/php_collections_me.h
index ade62c4..90e1f39 100644
--- a/src/php_collections_me.h
+++ b/src/php_collections_me.h
@@ -54,11 +54,7 @@ PHP_METHOD(Collection, keys);
 PHP_METHOD(Collection, last);
 PHP_METHOD(Collection, lastIndexOf);
 PHP_METHOD(Collection, map);
-PHP_METHOD(Collection, mapKeys);
-PHP_METHOD(Collection, mapKeysTo);
 PHP_METHOD(Collection, mapTo);
-PHP_METHOD(Collection, mapValues);
-PHP_METHOD(Collection, mapValuesTo);
 PHP_METHOD(Collection, max);
 PHP_METHOD(Collection, maxBy);
 PHP_METHOD(Collection, maxWith);
diff --git a/stubs/Collection.php b/stubs/Collection.php
index 8d4fd7f..251364d 100644
--- a/stubs/Collection.php
+++ b/stubs/Collection.php
@@ -39,7 +39,7 @@ class Collection implements ArrayAccess, Countable
      * Returns a collection containing key-value pairs provided by transform function applied
      * to elements of the given collection.
      *
-     * @param callable $transform ($value) -> Pair
+     * @param callable $transform ($value, $key) -> Pair
      * @return Collection
      */
     function associate($transform) {}
@@ -49,7 +49,7 @@ class Collection implements ArrayAccess, Countable
      * function applied to each element of the given collection.
      *
      * @param Collection $destination
-     * @param callable $transform ($value) -> Pair
+     * @param callable $transform ($value, $key) -> Pair
      * @return Collection
      */
     function associateTo($destination, $transform) {}
@@ -58,7 +58,7 @@ class Collection implements ArrayAccess, Countable
      * Returns a collection containing the elements from the given collection indexed by the key
      * returned from keySelector function applied to each element.
      *
-     * @param callable $key_selector ($value) -> $key
+     * @param callable $key_selector ($value, $key) -> $new_key
      * @return Collection
      */
     function associateBy($key_selector) {}
@@ -69,7 +69,7 @@ class Collection implements ArrayAccess, Countable
      * and value is the element itself.
      *
      * @param Collection $destination
-     * @param callable $key_selector ($value) -> $key
+     * @param callable $key_selector ($value, $key) -> $new_key
      * @return Collection
      */
     function associateByTo($destination, $key_selector) {}
@@ -398,62 +398,24 @@ class Collection implements ArrayAccess, Countable
     function lastIndexOf($element) {}
 
     /**
-     * Returns a collection containing the results of applying the given transform function
-     * to each element in the original collection.
+     * Returns a collection containing an array of values obtained by applying the transform function
+     * to each element of the original collection.
      *
-     * @param callable $transform ($value, $key) -> Pair
+     * @param callable $transform ($value, $key) -> $new_value
      * @return Collection
      */
     function map($transform) {}
 
     /**
-     * Returns a new collection with entries having the keys obtained by applying the transform function
-     * to each keys and values of this collection.
-     *
-     * @param callable $transform ($value, $key) -> $new_key
-     * @return Collection
-     */
-    function mapKeys($transform) {}
-
-    /**
-     * Populates the given destination collection with entries having the keys obtained by applying the
-     * transform function to each keys and values of this collections.
+     * Populates the given destination collection with an array of values obtained by applying the
+     * transform function to each element of the original collection.
      *
      * @param Collection $destination
-     * @param callable $transform ($value, $key) -> $new_key
-     * @return Collection
-     */
-    function mapKeysTo($destination, $transform) {}
-
-    /**
-     * Applies the given transform function to each element of the original collection and appends the
-     * results to the given destination.
-     *
-     * @param Collection $destination
-     * @param callable $transform ($value, $key) -> Pair
+     * @param callable $transform ($value, $key) -> $new_value
      * @return Collection
      */
     function mapTo($destination, $transform) {}
 
-    /**
-     * Returns a new collection with entries having the keys of this collection and the values obtained
-     * by applying the transform function to each entry in this collection.
-     *
-     * @param callable $transform ($value, $key) -> $new_value
-     * @return Collection
-     */
-    function mapValues($transform) {}
-
-    /**
-     * Populates the given destination collection with entries having the keys of this collection and
-     * the values obtained by applying the transform function to each entry in this collection.
-     *
-     * @param Collection $destination
-     * @param callable $transform ($value, $key) -> $new_value
-     * @return Collection
-     */
-    function mapValuesTo($destination, $transform) {}
-
     /**
      * Returns the largest element or null if there are no elements. The collection should contain
      * only one type of numeric elements(int/double).
diff --git a/tests/037-map.phpt b/tests/037-map.phpt
new file mode 100644
index 0000000..449ab8c
--- /dev/null
+++ b/tests/037-map.phpt
@@ -0,0 +1,18 @@
+--TEST--
+Test Collection::map() and Collection::mapTo().
+--FILE--
+<?php
+$array = ['foo' => 'bar', 'bar' => 'baz'];
+$collection = Collection::init($array)->map(function ($value, $key) {
+    return $key.$value;
+});
+if ($collection->toArray() != ['foobar', 'barbaz'])
+    echo 'Collection::map() failed.', PHP_EOL;
+$collection1 = Collection::init(['dummy']);
+$collection2 = Collection::init($array)->mapTo($collection1, function ($value, $key) {
+    return $value.$key;
+});
+if ($collection1->toArray() != $collection2->toArray() || $collection1->toArray() != ['dummy', 'barfoo','bazbar'])
+    echo 'Collection::mapTo() failed.', PHP_EOL;
+?>
+--EXPECT--