Stress testing is one of the preferred noninvasive methods of identifying patients with coronary artery disease (CAD). Its value in patients with coronary artery spasm (CAS) is, however, difficult to ascertain. The authors studied 91 consecutive patients with angiographically documented CAS. All patients underwent a symptom-limited bicycle exercise test before coronary angiography. Eight patients (8.8%) showed ST-segment elevation during exercise; 37 (40.7%), ST-segment depression; and 46 (50.5%), no changes. Thirty patients had normal coronary arteries; 19, one-vessel disease; 19, two-vessel disease; and 23, three-vessel disease. Stress testing yielded abnormal results in 7 of 30 patients (23%) with no CAD and in 38 of 61 (62%) with fixed CAD (p less than 0.01). ST-segment response to exercise did not correlate with most clinical findings such as age, type of angina, duration of pain episodes, or the degree of disease activity. However, a significant correlation was found with the extent and severity of CAD. Absence of ST changes or ST-segment elevation did not differentiate those patients with or without CAD, but only 4 of 37 patients with ST-segment depression had no significant fixed lesions. In conclusion, half of the patients with CAS had a normal stress test. ST-segment elevation is an uncommon finding in these patients and does not reliably differentiate those with and without fixed CAD. The only relevant finding of stress testing in CAS patients is ST-segment depression, which strongly suggests the presence of underlying CAD.