We evaluated the nutritional status of 120 hemodialysis patients using the urea kinetic model. Protein catabolic rate (PCR), an indirect measurement of dietary protein intake, and urea volume of distribution were calculated. Their mid-week predialysis BUN was targeted at 80 +/- 10 mg/dl. The risk factors for chronic hemodialysis patients were analyzed, and since the diabetic patients were unevenly distributed we took them out of the study. This report thus comprises 98 patients distributed in four groups according to their mean PCR and BUN: group 1, mean PCR of 0.63 g/kg/day and BUN of 51 mg/dl; group 2, mean PCR of 0.93 g/kg/day and BUN of 60 mg/dl; group 3, mean PCR of 1.02 g/kg/day and BUN of 79 mg/dl; group 4, mean PCR of 1.2 g/kg/day and BUN of 96 mg/dl. Patients in group 1 had a higher morbidity (number of hospitalizations and number of days in the hospital per patient per year) and a higher mortality (percent per year). The most common causes of hospitalization were infection and congestive heart failure. This group also had an unusually high incidence of pericarditis. Because their risk factors were similar to the other groups, the data suggest that malnutrition was the main cause of these patients' high morbidity and mortality. These patients must be considered at high risk and should be treated aggressively.