The determination of functional impairment is an important portion of the evaluation of patients with mitral stenosis and frequently is instrumental in the determination to proceed with invasive testing. To test the hypothesis that patients with slowly evolving disability from mitral stenosis frequently do not recognize the degree of their limitations and to determine the utility of formal exercise testing, 24 consecutive patients with pure or predominant mitral stenosis were evaluated for NYHA functional category (NYHA class) by historical determination of functional impairment, echocardiographic mitral valve area (echo MVA), exercise duration, estimated maximum oxygen consumption, and functional aerobic impairment during a symptom-limited Bruce protocol exercise test and multiple catheterization-derived parameters. The data revealed no difference in exercise duration or mitral valve area between NYHA classes, but demonstrated an excellent correlation between exercise duration and severity of mitral valve stenosis determined at cardiac catheterization (cath MVA). This relationship was similar to that of echo MVA to cath MVA and exceeded that of exercise time to any other parameter measured during catheterization. Estimation of maximum oxygen consumption or functional aerobic impairment did not improve the exercise duration to valve area relationship. The data presented thus demonstrate that Bruce protocol exercise testing is a valuable adjunct to other noninvasive tests in the initial evaluation of selected patients with mitral stenosis. By virtue of being easily repeated at low risk, exercise testing may also be useful in long term follow-up of medically treated mitral stenosis patients.