An investigation into the behavior of the Beeler-Reuter mathematical model of membrane electrical activity for ventricular myocardial fibers, especially with regard to rapid reexcitation, is presented. Two protocols were used: (a) the response of the model to a sudden change in the pacing interval for various stimulus strengths was analyzed; and (b) the strength-duration characteristics of the model for various coupling intervals were generated. The results indicate that the model is nearly exclusively responsive to the previous diastolic interval, and rather insensitive to the coupling interval. Both the action potential duration and amplitude can be modeled nearly perfectly by one-minus-double-exponential functions of the diastolic interval. However, contrary to some experimental evidence, the model is not reexcitable for cases when the premature stimulus is delivered while the transmembrane potential is greater than approximately -70 mV.