Fluidized-bed catalytic cracking (FCC) units, are one of the most complex and interactive processes in the refining industry, hence they are difficult to operate and to control; on the other hand they are one of the main producers of gasoline, which is an incentive to improve operation policies. Control of the FCC has been and continues to be a challenging and important problem. A control system is composed of several interacting control loops. The number of feasible alternative configurations of control loops is very large. Multiloop control systems are often used for industrial multivariable processes because of their simplicity. Relative gain array is used to minimize the interaction and to select the variable pairings. This work is concerned with the design of multivariable feedback control configurations for FCC units. Sufficient conditions to achieve regulation in terms of the steady-state gain matrix are provided, allowing to obtain a systematic procedure for analyzing multiloop control configurations of complex and interacting processes. Numerical simulations on a dynamical model based on a FCC unit operating in the partial-combustion mode are used to show the effectiveness of several control configurations under disturbances. (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.