To assess the predictive value of ventricular late potentials and programmed ventricular stimulation, 379 patients without a history of sustained ventricular tachycardia, dizziness or syncope were studied prospectively. Group I included patients referred for coronary angiography. Group II consisted of patients who survived an episode of acute myocardial infarction and who were studied within 6 weeks after onset. During follow-up (mean 13 months), 16 patients died. Six of these patients died suddenly within one hour. The prevalence of sudden cardiac death was lower (0.8%) in group I compared to group II (3.0%). There was no correlation between results of both methods and the subsequent occurrence of sudden cardiac death. Symptomatic sustained ventricular tachycardia was documented in 10 patients (2.6%). Only one patient in group I later developed symptomatic sustained ventricular tachycardia in contrast to nine cases in group II. Symptomatic sustained ventricular tachycardia could be predicted in patients in the early postmyocardial infarction period (group II). By using various combinations of parameters, the highest predictive value for subsequent sustained ventricular tachycardia was reached by the following combination: Late potentials of 40 ms duration or more, induction of monomorphic sustained ventricular tachycardia at rates below 270 beats min-1 and interval after myocardial infarction less than 6 weeks. In conclusion, both techniques seemed to be promising for the identification of patients at risk of ventricular tachycardia after myocardial infarction.