For the best clinical use of the treadmill exercise test, and to have rational expectations of it as a reliable diagnostic tool, sound understanding of the information provided by the test is needed. The electrocardiographic response to cardiopulmonary stress; blood pressure response; and workload, heart rate, and blood pressure achieved at peak exercise all are important indicators of exercise performance and must be considered when interpreting test results. Test results indicating the presence or absence and extent of coronary artery disease must be interpreted in the light of particular clinical factors, as diagnostic accuracy differs with patient populations. Diagnostic use of the treadmill test in patients with chest pain syndromes is reviewed, and issues that must be considered by the clinician in doing the test and evaluating its results are emphasized.