diff --git a/README.md b/README.md
index a21a603..f10f142 100644
--- a/README.md
+++ b/README.md
@@ -52,8 +52,10 @@ A PHP library with a variety of string manipulation functions with multibyte sup
     * [tidy](#tidy)
     * [titleize](#titleize)
     * [toAscii](#toascii)
+    * [toLowerCase](#tolowercase)
     * [toSpaces](#tospaces)
     * [toTabs](#totabs)
+    * [toUpperCase](#touppercase)
     * [trim](#trim)
     * [truncate](#truncate)
     * [underscored](#underscored)
@@ -744,6 +746,20 @@ S::create('fòô bàř')->toAscii();
 S::toAscii('fòô bàř');  // 'foo bar'
 ```
 
+#### toLowerCase
+
+$stringy->toLowerCase()
+
+S::toLowerCase(string $str [, string $encoding ])
+
+Converts all characters in the string to lowercase. An alias for PHP's
+mb_strtolower().
+
+```php
+S::create('FÒÔ BÀŘ', 'UTF-8')->toLowerCase();
+S::toLowerCase('FÒÔ BÀŘ', 'UTF-8');  // 'fòô bàř'
+```
+
 #### toSpaces
 
 $stringy->toSpaces([ tabLength = 4 ])
@@ -773,6 +789,20 @@ S::create('    fòô    bàř')->toTabs();
 S::toTabs('    fòô    bàř');  // '   fòô bàř'
 ```
 
+#### toUpperCase
+
+$stringy->toUpperCase()
+
+S::toUpperCase(string $str [, string $encoding ])
+
+Converts all characters in the string to uppercase. An alias for PHP's
+mb_strtoupper().
+
+```php
+S::create('fòô bàř', 'UTF-8')->toUpperCase();
+S::toUpperCase('fòô bàř', 'UTF-8');  // 'FÒÔ BÀŘ'
+```
+
 #### trim
 
 $stringy->trim()
diff --git a/src/Stringy/StaticStringy.php b/src/Stringy/StaticStringy.php
index 968533a..d147053 100644
--- a/src/Stringy/StaticStringy.php
+++ b/src/Stringy/StaticStringy.php
@@ -296,6 +296,32 @@ class StaticStringy
         return Stringy::create($str)->toTabs($tabLength)->str;
     }
 
+    /**
+     * Converts all characters in the string to lowercase. An alias for PHP's
+     * mb_strtolower().
+     *
+     * @param   string  $str       String to convert case
+     * @param   string  $encoding  The character encoding
+     * @return  string  The lowercase string
+     */
+    public function toLowerCase($str, $encoding = null)
+    {
+        return Stringy::create($str, $encoding)->toLowerCase()->str;
+    }
+
+    /**
+     * Converts all characters in the string to uppercase. An alias for PHP's
+     * mb_strtoupper().
+     *
+     * @param   string  $str       String to convert case
+     * @param   string  $encoding  The character encoding
+     * @return  string  The uppercase string
+     */
+    public function toUpperCase($str, $encoding = null)
+    {
+        return Stringy::create($str, $encoding)->toUpperCase()->str;
+    }
+
     /**
      * Converts the string into an URL slug. This includes replacing non-ASCII
      * characters with their closest ASCII equivalents, removing non-alphanumeric
diff --git a/src/Stringy/Stringy.php b/src/Stringy/Stringy.php
index 5a25dfd..23ec6be 100644
--- a/src/Stringy/Stringy.php
+++ b/src/Stringy/Stringy.php
@@ -548,6 +548,32 @@ class Stringy
         return $stringy;
     }
 
+    /**
+     * Converts all characters in the string to lowercase. An alias for PHP's
+     * mb_strtolower().
+     *
+     * @return  Stringy  Object with all characters of $str being lowercase
+     */
+    public function toLowerCase()
+    {
+        $str = mb_strtolower($this->str, $this->encoding);
+
+        return self::create($str, $this->encoding);
+    }
+
+    /**
+     * Converts all characters in the string to uppercase. An alias for PHP's
+     * mb_strtoupper().
+     *
+     * @return  Stringy  Object with all characters of $str being uppercase
+     */
+    public function toUpperCase()
+    {
+        $str = mb_strtoupper($this->str, $this->encoding);
+
+        return self::create($str, $this->encoding);
+    }
+
     /**
      * Converts the string into an URL slug. This includes replacing non-ASCII
      * characters with their closest ASCII equivalents, removing non-alphanumeric
diff --git a/tests/Stringy/CommonTest.php b/tests/Stringy/CommonTest.php
index 5a73daf..f89dfbb 100644
--- a/tests/Stringy/CommonTest.php
+++ b/tests/Stringy/CommonTest.php
@@ -338,6 +338,32 @@ abstract class CommonTest extends PHPUnit_Framework_TestCase
         return $testData;
     }
 
+    public function stringsForToLowerCase()
+    {
+        $testData = array(
+            array('foo bar', 'FOO BAR'),
+            array(' foo_bar ', ' FOO_bar '),
+            array('fòô bàř', 'FÒÔ BÀŘ', 'UTF-8'),
+            array(' fòô_bàř ', ' FÒÔ_bàř ', 'UTF-8'),
+            array('αυτοκίνητο', 'ΑΥΤΟΚΊΝΗΤΟ', 'UTF-8'),
+        );
+
+        return $testData;
+    }
+
+    public function stringsForToUpperCase()
+    {
+        $testData = array(
+            array('FOO BAR', 'foo bar'),
+            array(' FOO_BAR ', ' FOO_bar '),
+            array('FÒÔ BÀŘ', 'fòô bàř', 'UTF-8'),
+            array(' FÒÔ_BÀŘ ', ' FÒÔ_bàř ', 'UTF-8'),
+            array('ΑΥΤΟΚΊΝΗΤΟ', 'αυτοκίνητο', 'UTF-8'),
+        );
+
+        return $testData;
+    }
+
     public function stringsForSlugify()
     {
         $testData = array(
diff --git a/tests/Stringy/StaticStringyTest.php b/tests/Stringy/StaticStringyTest.php
index 5dd89df..17b9bd7 100644
--- a/tests/Stringy/StaticStringyTest.php
+++ b/tests/Stringy/StaticStringyTest.php
@@ -222,6 +222,26 @@ class StaticStringyTestCase extends CommonTest
         $this->assertEquals($expected, $result);
     }
 
+    /**
+     * @dataProvider stringsForToLowerCase
+     */
+    public function testToLowerCase($expected, $str, $encoding = null)
+    {
+        $result = S::toLowerCase($str, $encoding);
+        $this->assertInternalType('string', $result);
+        $this->assertEquals($expected, $result);
+    }
+
+    /**
+     * @dataProvider stringsForToUpperCase
+     */
+    public function testToUpperCase($expected, $str, $encoding = null)
+    {
+        $result = S::toUpperCase($str, $encoding);
+        $this->assertInternalType('string', $result);
+        $this->assertEquals($expected, $result);
+    }
+
     /**
      * @dataProvider stringsForSlugify
      */
diff --git a/tests/Stringy/StringyTest.php b/tests/Stringy/StringyTest.php
index b9704d2..5534b7a 100644
--- a/tests/Stringy/StringyTest.php
+++ b/tests/Stringy/StringyTest.php
@@ -285,6 +285,30 @@ class StringyTestCase extends CommonTest
         $this->assertEquals($str, $stringy);
     }
 
+    /**
+     * @dataProvider stringsForToLowerCase
+     */
+    public function testToLowerCase($expected, $str, $encoding = null)
+    {
+        $stringy = S::create($str, $encoding);
+        $result = $stringy->toLowerCase();
+        $this->assertInstanceOf('Stringy\Stringy', $result);
+        $this->assertEquals($expected, $result);
+        $this->assertEquals($str, $stringy);
+    }
+
+    /**
+     * @dataProvider stringsForToUpperCase
+     */
+    public function testToUpperCase($expected, $str, $encoding = null)
+    {
+        $stringy = S::create($str, $encoding);
+        $result = $stringy->toUpperCase();
+        $this->assertInstanceOf('Stringy\Stringy', $result);
+        $this->assertEquals($expected, $result);
+        $this->assertEquals($str, $stringy);
+    }
+
     /**
      * @dataProvider stringsForSlugify
      */