The effect of the long-term use of prolonged medicinal forms containing nitroglycerin (NG)--trinitrolong and nitroderm-TTS on the pharmacokinetics of sublingual NG was studied. A significant change of the pharmacokinetic parameters at the sublingual use of NG both after the long-term treatment with trinitrolong and after therapy with nitroderm was observed: in both cases the time of half-release of NG from plasma and the average time of retention increased, the area under the curve of concentration-time significantly increased and the drug clearance decreased (for trinitrolong the difference in the clearance parameter is significant). While combining the data on both drugs the difference in the last two parameters also becomes significant. The observed slowing of elimination is probably the cause of the development of tolerance to NH at the long-term treatment, since according to the modern notions the degree of the effect is determined by the rate of NG metabolism.