The hemodynamic effects of 10 and 20 mg isobutyl methyl 1,4-dihydro-2,6-dimethyl-4-(2-nitrophenyl)-3,5-pyridinecarboxylate (nisoldipine, Bay k 5552) p.o. were studied in 15 patients with chronic congestive heart failure due to ischemic heart disease or cardiomyopathy. The dose of 10 mg elicited only a decrease of pulmonary wedge pressure during exercise, all other parameters remained unaffected. After 20 mg nisoldipine arterial blood pressure was reduced already at rest. During exercise, arterial as well as pulmonary artery and wedge pressures were significantly reduced. Heart rate remained unaffected and cardiac index increased slightly. It is concluded, that nisoldipine improves the hemodynamic situation in chronic congestive heart failure by simultaneously reducing cardiac pre- and afterload.