The occurrence of maldigestion and malnutrition was studied in 14 patients who had undergone pancreaticoduodenectomy and occlusion of the Wirsung duct with Neoprene. Before discharge patients were put on a 70 g/day dietary fat intake. Mean faecal fat excretion was 32.9 g/day without enzyme replacement and fell to 14.2 g/day with pancrelipase supplementation. At discharge all patients were underweight (88 per cent of the usual mean body-weight) and nine patients showed alteration in laboratory nutritional parameters. At the time of discharge a low-fat diet (50 g/day) was prescribed. Six months after surgery, mean faecal fat excretion decreased further to 8.3 g/day (P less than 0.01) and all patients but one gained weight, reaching 93 per cent of the usual mean body-weight with normalized nutritional parameters. Our data show that the combination of enzyme replacement therapy and low-fat diet allows good correction of steatorrhoea and a significant improvement in nutritional status.