diff --git a/.gitignore b/.gitignore
index 80a01ec..5428831 100644
--- a/.gitignore
+++ b/.gitignore
@@ -15,4 +15,6 @@ node_modules
 npm-debug.log
 
 build
-.lock-wscript
\ No newline at end of file
+.lock-wscript
+
+.idea
\ No newline at end of file
diff --git a/Readme.md b/Readme.md
index e71ac65..4d712a2 100644
--- a/Readme.md
+++ b/Readme.md
@@ -15,12 +15,27 @@ npm install base62
 
 ## Usage
 
+### Default Character Set Example
+
 ```javascript
 Base62 = require('base62')
 Base62.encode(999)  // 'g7'
 Base62.decode('g7') // 999
 ```
 
+### Custom Character Set Example
+
+The default character set is `0-9a-zA-Z`. This can be updated to a custom character set. Naturally, it must be 62 characters long.
+
+Instead of the character set `0-9a-zA-Z` you want to use `0-9A-Za-z`, call the `setCharacterSet()` method on the Base62 object passing in the string `"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"`. Note that all characters must be unique.
+
+```javascript
+Base62 = require('base62')
+Base62.setCharacterSet("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz");
+Base62.encode(999)  // 'G7'
+Base62.decode('G7') // 999
+```
+
 ## Development
 
 Source hosted at [GitHub](http://github.com/andrew/base62.js).
diff --git a/base62.js b/base62.js
index 221a1d9..8b0ec2b 100644
--- a/base62.js
+++ b/base62.js
@@ -1,25 +1,38 @@
-module.exports = (function (my) {
-  my.chars = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".split("");
-
-  my.encode = function(i){
-    if (i === 0) {return '0';}
-    var s = '';
-    while (i > 0) {
-      s = this.chars[i % 62] + s;
-      i = Math.floor(i/62);
-    }
-    return s;
-  };
-  my.decode = function(a,b,c,d){
-    for (
-      b = c = (
-        a === (/\W|_|^$/.test(a += "") || a)
-      ) - 1;
-      d = a.charCodeAt(c++);
-    )
-    b = b * 62 + d - [, 48, 29, 87][d >> 5];
-    return b;
-  };
-
-  return my;
+module.exports = (function (Base62) {
+    var DEFAULT_CHARACTER_SET = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
+
+    Base62.encode = function(integer){
+        if (integer === 0) {return '0';}
+        var s = '';
+        while (integer > 0) {
+            s = Base62.characterSet[integer % 62] + s;
+            integer = Math.floor(integer/62);
+        }
+        return s;
+    };
+
+    Base62.decode = function(base62String){
+        var val = 0, base62Chars = base62String.split("").reverse();
+        base62Chars.forEach(function(character, index){
+            val += Base62.characterSet.indexOf(character) * Math.pow(62, index);
+        });
+        return val;
+    };
+
+    Base62.setCharacterSet = function(chars) {
+        var arrayOfChars = chars.split(""), uniqueCharacters = [];
+
+        if(arrayOfChars.length != 62) throw Error("You must supply 62 characters");
+
+        arrayOfChars.forEach(function(char){
+            if(!~uniqueCharacters.indexOf(char)) uniqueCharacters.push(char);
+        });
+
+        if(uniqueCharacters.length != 62) throw Error("You must use unique characters.");
+
+        Base62.characterSet = arrayOfChars;
+    };
+
+    Base62.setCharacterSet(DEFAULT_CHARACTER_SET);
+    return Base62;
 }({}));
diff --git a/test/test.js b/test/test.js
index 36509dd..be4e184 100644
--- a/test/test.js
+++ b/test/test.js
@@ -2,13 +2,73 @@ var assert = require('assert');
 var Base62 = require('../base62');
 
 describe("encode", function() {
-  it("should encode a number to a Base62 string", function() {
-    assert.equal(Base62.encode(999), 'g7');
-  });
+    it("should encode a number to a Base62 string", function() {
+        assert.equal(Base62.encode(999), 'g7');
+        assert.equal(Base62.encode(65), '13');
+        //test big numbers
+        assert.equal(Base62.encode(10000000000001), "2Q3rKTOF");
+        assert.equal(Base62.encode(10000000000002), "2Q3rKTOG");
+
+    });
 });
 
 describe("decode", function() {
-  it("should decode a number from a Base62 string", function() {
-    assert.equal(Base62.decode('g7'), 999);
-  });
+    it("should decode a number from a Base62 string", function() {
+        assert.equal(Base62.decode('g7'), 999);
+        assert.equal(Base62.decode('13'), 65);
+        //test big numbers
+        assert.equal(Base62.decode("2Q3rKTOF"), 10000000000001);
+        assert.equal(Base62.decode("2Q3rKTOH"), 10000000000003);
+    });
 });
+
+describe("setCharacterSequence", function(){
+    it("should update the character sequence", function(){
+        Base62.setCharacterSet("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz");
+
+        //Test default character set is not intact
+        assert.notEqual(Base62.encode(999), 'g7');
+
+        //Test new character set test cases
+        var testCases = {
+            "G7": 999,
+            "Lxf7": 5234233,
+            "qx": 3283,
+            "29": 133,
+            "1S": 90,
+            "3k": 232,
+            "4I": 266,
+            "2X": 157,
+            "1E": 76,
+            "1L": 83
+        };
+
+        Object.keys(testCases).forEach(function(base62String){
+            assert.equal(Base62.encode(testCases[base62String]), base62String);
+            assert.equal(Base62.decode(base62String), testCases[base62String]);
+        });
+
+    });
+
+    it("should throw exceptions on invalid strings", function(){
+        var errorCheck = function(err) {
+            if ( (err instanceof Error) && /value/.test(err) ) {
+                return true;
+            }
+        };
+
+        assert.throws(function(){
+            Base62.setCharacterSet("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxy");
+        }, /You must supply 62 characters/);
+
+        assert.throws(function(){
+            Base62.setCharacterSet("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz;");
+        }, /You must supply 62 characters/);
+
+
+        assert.throws(function(){
+            Base62.setCharacterSet("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxzz");
+        }, /You must use unique characters/);
+
+    });
+});
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