The complex pathophysiology of human arrhythmias has proven difficult to model. Direct correlations between the traditional arrhythmia mechanisms, including abnormal excitability, conduction, or repolarization and underlying molecular or cellular biology are poorly defined, as the primary etiologies of many human arrhythmias remain unknown. Since the causes of several arrhythmic syndromes have been identified, genetic models reproducing the mechanisms of these arrhythmias have become feasible. Initial murine modeling has revealed that in many cases the pathophysiology of the respective human disease is more complex than had been suspected. Insights from human genetic studies and animal models strongly suggest that the primary molecular defects may contribute at many stages in the causal chain leading to arrhythmia. The comprehensive analysis of each arrhythmia will require knowledge not only of the membrane effects of the primary defects, but also downstream intracellular signals, the developmental results of these perturbations, and the integration of compensatory responses and environmental factors. Precise modeling will require not only the mutation of specific residues in known disease genes, but also the systematic study of each of the many steps in arrhythmogenesis. Ultimately, such models will enable unbiased screens for disease mechanisms and novel therapies.