The MIMO Toolbox is a collection of Matlab functions and a GUI. Its purpose is to complement the Control Toolbox for Matlab with functions capable of handling the multivariable input-output scheme.The MIMO Toolbox was developed for Matlab 7.
The gui, icdtool, is a MIMO design utility based on Individual Channel design for 2x2 systems.
I've included a .pdf document that contains the function reference, along with a brief explanation of the theory behind the functions. I recommend you read it, as the information provided is quite useful.