Two mathematical models were presented as an arrhythmia generator. One was the so-called modulated parasystole model. The other was a model of the rate-dependent property of atrioventricular nodal conduction represented by the atrioventricular recovery curve (AVRC). Both models were mathematically formulated as a nonlinear first-order difference equation, and implemented on a personal computer (PC) as an arrhythmia simulator. It was utilized for evaluating the diagnostic performance of computerized ECG analyzers.