This paper presents a new method for constructing empirical, two-state-variable models of cardiac cell membrane kinetics. The formulation is based on nonuniform rational B-spline surfaces that can be manipulated interactively to produce desired action potential (AP) properties. Using this new methodology, a model of the guinea pig ventricular action potential was constructed that reproduces experimentally measured relationships between pacing cycle length and action potential duration and conduction velocity. The model is computationally efficient, requiring about sixfold less CPU time than the Beeler-Reuter ionic model and only about twice as much time as a FitzHugh-Nagumo type empirical model. Thus, for modeling propagation phenomena, this method can produce models that improve on the quantitative accuracy of both simple empirical models and elaborate ionic models, with computational cost comparable to the simplest of empirical models. © 2000 IEEE Publisher Item Identifier S 0018-9294(00)04414-1.