An interactive Pascal program for use in the IBM-PC and compatible computers is presented. It simulates the activation of integral membrane proteins involved in ionic transport. The program allows variation of the number of transport proteins, ionic concentrations, permeability ratios, voltage dependence of permeabilities and temperature. A separate procedure for simulation of Na+-K+ pumps has been included considering their relevance in physiology. The main purpose of the present program is to serve as a teaching aid to understand the basic principles and concepts related with the electrogenesis and the stoichiometry of membrane transport processes.