To determine the clinical status, the occurrence of chronic ambulatory arrhythmias, and the prognosis of patients with exercise-induced ventricular tachycardia, 26 patients with ventricular tachycardia during or immediately following exercise on a treadmill were evaluated. Of the 26 patients, 16 had coronary arterial disease, two had nonischemic cardiomyopathy, and eight had no other cardiac disease. Eleven (61 percent) of the 18 patients with heart disease developed ventricular tachycardia during exercise, in contrast to six (75 percent) of eight normal subjects who had ventricular tachycardia after exercise. In eight patients with repeat stress testing, four (50 percent) had reproducible ventricular tachycardia or malignant ventricular ectopic beats. In 19 (73 percent) of 29 patients, malignant ventricular ectopy occurred on random 24-hour electrocardiographic monitoring; ventricular tachycardia occurred in 5/26 (19 percent), and malignant ventricular ectopic beats occurred in 14/26 (54 percent). Fifteen (83 percent) of 18 patients with cardiac disease vs 4 (50 percent) of eight normal subjects (P less than 0.05) evidenced malignant ventricular ectopy during ambulatory monitoring. Only one episode of sudden cardiac death occurred in 24 patients followed for 21 months. Thus, 30 percent (eight) of the patients with exercise-induced ventricular tachycardia had no evidence of heart disease. Furthermore, exercise-provoked ventricular tachycardia presaged sudden death in only one of 24 patients; however, ventricular tachycardia with exercise correctly predicts the presence of chronic advanced ventricular ectopic beats or ventricular tachycardia in 73 percent (19/26) of the patients.