A clinician is faced with several dilemmas when evaluating the asymptomatic individual. The first dilemma relates to 'who should be evaluated'. Generally the first step in evaluation is the exercise stress test (fig. 2). The following are guidelines that can be used to systematically evaluate the individual asymptomatic patient who presents with a 'positive exercise stress test' (fig. 3). An ambulatory ECG can be performed to evaluate the occurrence and frequency of asymptomatic ST segment depression and the response to nitrates. Isotope angiography and exercise 201Tl perfusion studies may provide additional information relating to the physiologic significance of asymptomatic ST segment depression. If these studies are negative and the patients' 'positive stress test' was obtained at a high cardiac workload coupled with rapid normalization of the ST segment after exercise, and there was no change in the ST segment depression after nitroglycerin, a reasonable case can be made to simply observe the patient. If the exercise test is 'positive' at a low cardiac workload, associated with prolonged ST segment depression and/or a 'positive' exercise thallium or positive exercise angiography, or there was change in the ST segment depression after nitroglycerin or a lifethreatening arrhythmia developed, coronary angiography seems warranted.