MathType represents characters internally using the MTCode encoding. MTCode is a superset of the Unicode encoding that uses Unicode's Private Use Area to represent mathematical characters that are not part of Unicode proper.

The tables whose links are shown below document MTCode's use of Unicode's Private Use Area (PUA). For the non-Private Use Area characters, please consult The Unicode Standard from Addison-Wesley. This book is available from good computer book stores or from Amazon.com. Please bear in mind that MTCode is based on Unicode 2.0, whereas Unicode 4.0 is the latest version of the standard. The newer versions of the standard mostly contain additional characters over earlier versions.