The present study examined the hemodynamic and metabolic effects of nutrition support in patients with malnutrition secondary to severe mitral valve disease and congestive heart failure. Pulmonary artery pressure measurements, echocardiographic studies, gas exchange measurements, immune function tests, and clinical evaluations were made on hospitalized patients 2 weeks before and 3 weeks after surgery for valve replacement or annuloplasty. All patients received a total daily energy intake of 20 to 30 kcal/kg, four of the patients preoperatively as a combination of oral food plus parenteral nutrition and these four patients plus two additional patients as only parenteral nutrition in the early postoperative period. All six patients received nutrition support as oral food plus parenteral nutrition in the late postoperative period. Compared with baseline, nutrition support was associated with stable hemodynamic function, unchanged whole-body oxygen consumption and carbon dioxide production, and improved clinical indices both before and after surgery. Comprehensive hemodynamic, metabolic, and clinical studies thus indicate that acceptable levels of nutrition support can be provided to malnourished patients with severe congestive heart failure, which improves their clinical status and does not adversely influence cardiac function.