A relatively simple model of optimum degree of sophistication for riser-reactor industrial fluid catalytic cracking (FCC) units is developed. An efficient iterative computer code is developed for the solution of the nonlinear two-point boundary value model equations. Sets of data for three industrial units are used to adjust the parameters of the model. Independent sets of data for each unit are used to verify the reliability of the model without any adjustable parameters. The model is used to investigate the static bifurcation behavior and its implications for design, operation, and control.