Ten patients with chronic congestive heart failure were studied to assess the hemodynamic effects and bioavailability of a transdermal nitroglycerin delivery system. Nitrate sensitivity was defined by a prior 20 minute infusion of nitroglycerin, 21 micrograms/min. Five patients with a satisfactory hemodynamic response to intravenous nitroglycerin received two nitroglycerin patches of 10 cm2 each and five patients who did not achieve a satisfactory response to intravenous nitroglycerin (that is, greater than or equal to 25% reduction in left ventricular filling pressure) received larger doses of transdermal nitroglycerin. In the five nitrate-sensitive patients who received 20 cm2 of transdermal nitroglycerin, one study was terminated at 90 minutes, at which point there was no detectable hemodynamic response or arterial plasma nitroglycerin evident. Two patients had a minimal hemodynamic response and a peak plasma concentration of 1 ng/ml. A fourth patient had a short-lived hemodynamic response at 60 and 120 minutes and a plasma nitroglycerin concentration of 1 ng/ml at 60 minutes. A fifth patient had a hemodynamic response persisting for 24 hours and plasma concentrations between 0.6 and 1.1 ng/ml. The remaining five patients showed little or no hemodynamic response despite doses of transdermal nitroglycerin from 40 to 60 cm2. The highest plasma concentration achieved in these patients was 2 ng/ml and there was no relation between dose administered and plasma concentration achieved. In 4 of the 10 patients who subsequently received nitroglycerin ointment, there were a greater decrease in left- and right-sided filling pressures and greater increase in plasma nitroglycerin concentrations (from 1.6 to 4.8 ng/ml) than those that occurred with transdermal nitroglycerin.(ABSTRACT TRUNCATED AT 250 WORDS)