Fourier analysis of the partial differential equations which govern the response of potentiometric enzyme electrodes has been used to determine the transient behavior of the electrode potential. When the enzyme reaction Is first-order the response Is dictated by two dimensionless terms, Dt/L2 and KMD/VL2. When the specific enzyme activities are reasonable, the electrode will be within a millivolt of Its final value when Dt/L2 Is greater than 1.42. In the analytically important region, the response time is virtually independent of the specific activity on the electrode. The behavior In the limit of a zero-order reaction has also been studied. In this case, the enzyme concentration has no Influence whatsoever on the transient behavior which is governed entirely by diffusion but it does of course influence the steady-state potential.