Forty patients (35 men and five women) who experienced hypotension during maximal symptom-limited exercise test were retested after a 12 +/- 4-month interval. Mean age was 53.5 years. All patients had multiple-vessel disease. Seventeen patients underwent coronary artery bypass surgery because of disabling angina, and 23 patients without disabling angina continued under medical management. At entry, there were no significant differences in age, left ventricular function or exercise performance between the medical and surgical groups. At follow-up, the surgical group showed an average increase in the exercise duration of 2.2 +/- 1.7 minutes (p less than 0.001), maximal heart rate of 17 +/- 15 beats/min (p less than 0.001), maximal systolic blood pressure of 26 +/- 23 mm Hg (p less than 0.001) and maximal rate-pressure product of 60 +/- 41 (p less than 0.001). These measurements did not change significantly in the medically managed group. Exercise-induced hypotension is apparently caused by ischemic left ventricular dysfunction, since in the majority of patients, it is reversible after successful revascularization. This observation is supported by the lack of improvement in a comparable group of patients managed without surgery.