The influences of nonuniform activity distribution within a porous solid support on the apparent kinetic parameters, V(m)app and K(m)app, of immobilized enzyme reactions following the Michaelis-Menten kinetics were theoretically investigated. As the enzyme is distributed to the neighborhood of the external surface of the support, V(m)app and K(m)app approach their respective intrinsic values over a wide range of substrate concentration. There is a close relationship between the nonuniform distribution and internal diffusional resistance. Changes in these two factors provide similar effects on V(m)app and K(m)app. As long as the immobilized enzyme reaction follows Michaelis-Menten kinetics, the nonuniform activity distribution never makes K(m)app less than its intrinsic value.