The incidence and pattern of ventricular arrhythmias in acute, subacute, late hospital and posthospital periods of myocardial infarction were investigated, using Holter monitoring, in 121 patients with large-focal and transmural myocardial infarction. A high incidence of complex ventricular arrhythmias was noted after the transfer from intensive care unit (38.8%). The relationship of complex ventricular arrhythmias to ventricular arrhythmias at previous stages was reviewed. Factors contributing to arrhythmias at different stages of myocardial infarction were analysed; the informative value of clinical signs and electric myocardial instability parameters was assessed. Signs having the greatest predictive power were identified, and risk indices for the development of arrhythmias during the subacute and late hospital stages of myocardial infarction were established using linear discriminant analysis, to enable identification of patients at risk of developing ventricular arrhythmias.