Reviewed here are the data from 34 patients given prazosin for chronic intractable heart failure. In 13 patients in whom hemodynamics were measured after the fifth 3 mg dose of prazosin was given, no attenuation was found. The cardiac index increased from 1.77 +/- 0.13 to 2.5 +/- 0.13 liters/min/m2 (p less than 0.001), and the pulmonary capillary wedge pressure decreased from 31,46 +/- 1.56 to 23.54 +/- 1.11 mg Hg (p less than 0.001). During long-term follow-up (15.9 +/- 1.5 months) the administration of spironolactone proved to be very useful. Within three months of starting prazosin therapy, none of the 15 patients discharged on a regimen of spironolactone needed readmission for edema, but 11 of the 13 patients discharged without a spironolactone regimen did. The addition of spironolactone or an increase in furosemide to the therapeutic regimen was helpful but a change to hydralazine was not. We concluded that prazosin causes short-term hemodynamic and long-term clinical improvement in patients with intractable heart failure; that spironolactone helps to prevent clinical attenuation but that more detailed studies are required to better characterize the attenuation to vasodilators seen in patients with congestive heart failure.