Using submaximal exercises, work capacity of 375 aircraft crewmembers, aged 20-49, was investigated. It declined slightly with age. The factors most frequently causing its decrease in healthy and diseased people were identified and methods of its measurement were refined. It was shown that the work load, chronotropic reserve index and cardiac index may give indirect evidence of the coronary blood flow rate, and the inotropic reserve index of the cardiac contractile function. Determination of work capacity of the flight personnel makes it possible to improve the medical supervision, detect at an early stage cardiovascular abnormalities and to substantiate expertise conclusions.