Assessment of functional capacity, of ability and disability among patients with cardiovascular disease raises a number of problems and issues for which there are currently only imperfect or incomplete answers. Emphasis must be placed on the lack of predictable relationship of anatomic abnormality and functional abnormality. For example, the percentage obstruction of the coronary artery documents the anatomic extent of the disease, rather than the limitation of functional capacity; the same lack of predictive value characterizes the decrease in resting ventricular ejection fraction. The response to a challenge of activity or exertion currently appears to offer the optimal method of assessing functional capacity for work, although a brief continuous exercise test may not be the optimal exercise protocol by which to evaluate endurance. As an example, in our laboratory, comparing a low-level continuous exercise test protocol with one with an intermittent exercise design (i.e., periods of exercise alternating with periods at rest), patients typically can perform at least one additional stage of exercise on the discontinuous or intermittent test protocol. This occurred without significant differences in the final heart rate, blood pressure, or rate-pressure product, probably because most patients so tested were limited not by myocardial ischemia but by musculoskeletal problems, fatigue, or dyspnea (8). An unmet need is a comparison of exercise test protocols for the assessment of functional capacity, possibly the development of new test protocols for patients with limited functional capacity, and the evaluation of the relationship of these test data to eight hours of occupational activity in the workplace setting. It appears logical that a diagnostic exercise test should differ from one designed to determine functional capacity, but the results of a variety of exercise test protocols should be compared with the actual physical activity able to be performed in the workplace, as well as with reported symptoms. It should be defined whether testing is to be performed on optimal medical therapy, which I believe should be the case; or whether the technique used for diagnostic exercise testing, that of the minimal medication possible, is to be employed. Next, the time after surgical intervention or following a prolonged hospitalization at which to test should be delineated in that the deconditioning effect of immobilization may substantially decrease effort tolerance, unrelated to the severity of the underlying cardiovascular disease. Finally, should exercise rehabilitation be recommended or required before testing for cardiovascular impairment; major improvement in functional capacity has occurred in previously sedentary patients with a variety of cardiovascular diseases, including those with important manifestations of myocardial ischemia and ventricular dysfunction.(ABSTRACT TRUNCATED AT 400 WORDS)