A model has been developed to describe the performance of a packed‐bed coimmobilized biochemical reactor. Each step in the consecutive reaction is assumed to follow Michaelis—Menten type kinetics. The model includes all the limiting steps controlling the rate of reaction and the additional effect of axial dispersion of bulk liquid. The model equations are solved by the explicit finite difference method from the transient to steady‐state condition. The effects of various parameters of physical importance on the reactor performance are discussed. Copyright © 1990 Society of Chemical Industry