The potentialities of hand isometric exercise (HIE) were studied in 84 patients with unstable angina pectoris and 25 with stable angina. With HIE, the coronary and contractile reserve was measured in the patients with angina. Lower exercise tolerance was revealed in the patients with unstable angina than in those with stable one. Among the patients with unstable angina, those at risk for myocardial infarction were predominant. Lower exercise tolerance appeared as decreased "threshold" double product values and diminished myocardial contractile reserve (higher left ventricular filling pressure). HIE applied in the study evaluates the efficacy of treatment and the prediction of the disease course more accurately.