The increasing amounts of initial capital investments in the chemical and petroleum industry are making accurate and realistic economic analyses a necessity. The purpose of this investigation was to develop a general economic evaluation model which was an improvement over previous analysis techniques. The new aspect of this model is its capability of analysing multiple investments with a comprehensive risk analysis and with a short computer running time. Significant features of the analysis technique include: (1) A general and flexible computer model which can easily be applied to a wide range of capital investment decisions, (2) The use of present value for a consistent and realistic economic evaluation criterion, (3) Consideration of the future economic environment through the capability of predicting the time-dependent changes of the main variables, (4) Monte Carlo risk analysis to determine the effect of uncertainty in the 14 main variables, (5) Two-plant analysis with the advantage of a delayed decision on the second plant, and (6) Execution in a relatively short computer running time (six minutes on IBM 360, 65). / Master of Science