The agreement between the results of standard ECG (CX) and cardiopulmonary (CPX) exercise stress tests performed in randomized sequence was evaluated in 40 patients with known coronary artery disease but who were not taking cardioactive therapy. Systolic blood pressure and heart rate were significantly higher during CPX only at low workload (less than 100 W). Exercise time and rate-pressure product at both peak exercise and ischaemic threshold were not significantly different between the two tests, even though their variability exceeded the value of 20%, which is generally accepted as the cut-off point for defining CX parameters as reproducible. However, the metabolic response to exercise, assessed by means of blood lactate kinetics analysis, was highly reproducible between the two tests. We conclude that the provocative role of exercise testing is not altered by the gas exchange analysis technique used in CAD patients. However, the common indexes of myocardial as well as of global physical performance may be influenced, thus requiring caution in comparing data with those derived from CX or from reference values.