The dose requirement for 95% depression of twitch tension and the time course of the neuromuscular blocking effects of the ED95 of pancuronium bromide and vecuronium bromide were studied during intravenous infusion of glucose, 5%, and nitroglycerin, 1 μg•kg-1•min-1, in 20 cats anesthetized with pentobarbital. Nitroglycerin administered continuously starting 1 hr before the administration of the ED95 and maintained during at least five maintenance doses of either pancuronium or vecuronium did not significantly potentiate the action of the neuromuscular blocking drugs, nor did it alter their time course of action. A tendency for a decrease (statistically not significant) rather than an increase in the duration of action of maintenance doses of both pancuronium and vecuronium was apparent during the treatment with nitroglycerin. These findings indicate a lack of interaction between pancuronium or vecuronium and nitroglycerin, provided that moderate doses are used.