An environment has been developed in which the computer algebra software Mathematica is used for the analysis of dynamic systems with models constructed through the graphical user interface (GUI) of the simulation software SIMULINK. The SIMULINK models are passed to Mathematica through MATLAB and MathLink programs under the control of a simple GUI. An application is described in which block-oriented nonlinear systems defined in SIMULINK are passed to Mathematica for analysis by multidimensional transforms. Mathematica procedures are used to determine the multidimensional transfer functions that relate the system outputs to the system inputs and these are used to obtain the time responses and the harmonic responses of the system. The method is illustrated for a feedback control system with a saturation characteristic in the forward path.