The association between ventricular ectopic activity (VEA) and ischemic episodes during everyday activities was investigated in ambulatory patients with stable angina pectoris. Seventy-five consecutive patients with proven coronary artery disease, ischemic episodes on Holter monitoring and positive treadmill tests, but without known ventricular arrhythmias, were prospectively studied. In these 75 patients, a total of 719 ischemic episodes were recorded during 127 twenty-four-hour monitoring periods. Forty-three patients had either no or only very low baseline VEA (less than 14 ventricular premature complexes [VPCs]/24 hours); none of these patients had increased VEA during any ischemic episode. However, among 32 patients who had greater than or equal to 14 VPCs/24 hours (average 243 VPCs/24 hours), increased VEA during ischemic episodes was observed in 11 (31%). These 11 patients had a total of 174 ischemic episodes and the increased VEA appeared in 47 (27%) of the episodes. During 40 of the ischemic episodes the number of single VPCs increased significantly compared to the baseline background VEA: during 4 episodes trigeminy appeared and during another 3 bigeminy was observed. More complex VEA was not observed. Among the 11 patients with increased VEA, only 4 developed VPCs during treadmill testing. No correlation was found between the severity of the ischemic episodes (degree of ST depression and duration of ischemia) and the increased VEA. In 83% of these episodes the increased VEA appeared during the last (possibly reperfusion) phase. No correlation was found between the appearance of ventricular arrhythmias during ischemic episodes and the presence or absence of chest pain at the same time.(ABSTRACT TRUNCATED AT 250 WORDS)