The version 2.4 of the LTI System Identificantion Toolbox is recommended with Matlab 7.4 (R2007a) or higher. Although Matlab 7.1, 7.0, 6.5 and 5 should also work (except the compilation of mex-files). The m-files should work on all platforms. The mex-files can be compiled under Windows, OS X and Linux, other platforms have not been checked.