In 113 patients with coronary disease finger rheoplethysmography was used to study the duration of the hemodynamic effect of nitroglycerin drugs of prolonged action (NDPA) as compared to placebo. Nitrong and sustac in doses of 2.5 and 2.6 mg, respectively, were effective 1 1/2 and 2 h, on the average; in doses of 6.5 and 6.4 mg--4 1/2 and 3 1/2 h, and in doses of 13 and 12.8 mg--5 1/2 and 4 1/2 h, respectively. The duration of the effect of NDPA and nitroglycerin (0.5 mg) given sublingually varied greatly in some patients from entire absence of any effect to rather prolonged action. The duration of NDPA and nitroglycerin (0.5 mg) action closely correlated, which enables prognosing the hemodynamic effect of NDPA.