Seventeen patients (pts) after myocardial infarction (MI) were studied with signal-averaged electrocardiograph and cardiac programmed electrical stimulation (PES). In 7 pts with late potentials (LPs), sustained ventricular tachycardia (SVT) was induced in 6 cases (6/7, 85.7%); while it was induced only in 3 cases the 10 pts without LPs (3/10, 30%). Both have significant difference (P less than 0.01). During following observation, pts with LPs and SVT induced 5 of the 6 appeared clinical SVT or ventricular fibrillation (VF) repetitiously, and 1 died from sudden cardiac death. They also have significant difference (P less than 0.001) with pts without LPs and SVT not induced. These results suggests that LPs is a significant index for predicting future events and its combination with PES is helpful to screen high-risk pts after MI.