The effect of nonuniform activity distribution in a porous support on the apparent kinetic parameters, <(V) over cap(m)(app) and (K) over cap(m)(app), of a packed-bed immobilized enzyme reactor has been theoretically investigated. (V) over cap(m)(app) and (K) over cap(m)(app) increase with the increase of external diffusional resistance, regardless of the type of nonuniform activity distribution. As the external diffusional resistance becomes significant, the apparent kinetic parameters became less dependent on the substrate concentration at the reactor inlet. Like the case of diffusional resistance or electrostatic field, the nonuniform activity distribution had a significant effect on (K) over cap(m)(app).