The original MOUSE (Modular Oriented Uncertainty SystEm) system was designed to deal with the problem of uncertainties in Environmental engineering calculations, such as a set of engineering cost or risk analysis equations. It was especially intended for use by individuals with little or no knowledge of computer languages, programming, or simulation. The MOUSE system runs on MS-DOS based personal computers. It is easy and fast to learn and has all of the features needed for substantive uncertainty analysis, such as built-in probability distributions, plotting and graphing capabilities, sensitivity analysis, and interest functions for cost analyses. A series of unique companion utility programs help (1) analyze sample data to determine the probability distributions that best fit those data and (2) check each program for errors in syntax. AutoMOUSE is a significant improvement to the original MOUSE system. It actually writes the computer program necessary to carry out the uncertainty analysis. The input to AutoMOUSE consists of the equations of the model and requires no knowledge of computer programming. It is designed primarily for beginners but is also of value for those who have some programming experience and wish to construct MOUSE programs quicker and with fewer errors.