The occurrence of malnutrition and maldigestion was studied in nine patients who underwent pancreatoduodenectomy and sclerosis of the residual pancreatic stump with neoprene. The operation causes a complete loss of exocrine pancreatic function, but spares islet cell function. Upon discharge from the hospital, patients received pancreatin powder as a dietary enzyme supplement (18,000 lipase U/meal). Patients were again hospitalized 2 y after surgery for evaluation of nutritional status and digestive function (hospital checkup). Nutritional status was evaluated by measuring serum albumin, total iron binding capacity, and total lymphocytes. Digestive function was assessed by the D-xylose tolerance test and determination of fecal fat excretion. Patients were then discharged with pancrelipase enteric-coated microspheres (ECM) as a dietary enzyme supplement (16,050 lipase U/meal). Malnutrition, defined as the occurrence of at least two abnormal nutritional parameters, was observed in three patients at the time of the hospital checkup. Upon reevaluation of nutritional status after 6 mo on pancrelipase ECM, all patients were well nourished. The mean body weight, which had been 52.8 Kg immediately after surgery, increased to 54.9 Kg at the time of the hospital checkup (p less than 0.01) and to 58.0 Kg after six months of pancrelipase ECM therapy (p less than 0.05). At the hospital checkup, the D-xylose test was normal in all patients and steatorrhea had decreased from a mean of 32.8 g/d without enzyme supplementation to 16.7 g/d with pancrelipase therapy (16,050 lipase U/meal). The complete loss of exocrine pancreatic function following surgery was well tolerated. In fact, when patients were on pancrelipase therapy, much of the original body weight was recovered and the biochemical indices of malnutrition were normalized.