We studied the effects of stopping long-term vasodilator therapy in 17 patients with chronic stable aortic insufficiency. These patients received hydralazine for 37 +/- 15 months (mean +/- SD) and, as a result, had experienced a significant decrease in left ventricular volumes. All patients were followed clinically and ten of the patients underwent serial radionuclide evaluation at baseline, while receiving drug, and at 20 +/- 7 months after stopping drug therapy. No patient showed evidence of acute clinical deterioration when drug therapy was stopped. The rate of progression to valve replacement due to onset of symptoms or left ventricular dysfunction was not significantly different from that previously reported in a population with similar characteristics. Left ventricular size, however, returned to levels similar to baseline after drug therapy was stopped. We conclude that long-term vasodilator therapy may be discontinued in patients with chronic stable aortic insufficiency without causing clinical deterioration or significant alteration in rate of progression to valve replacement.