We have compared the metabolic consequences of two forms of exocrine drainage for pancreaticoduodenal transplant, duodenojejunostomy (DJ) and duodenocystostomy (DC). DC offered the advantage of avoiding opening of the recipient small intestine with its potential for wound sepsis, as well as a reliable method for early detection of pancreatic rejection as measured by an abrupt fall in urinary amylase and bicarbonate concentration. However, DC led to a large urinary loss of bicarbonate with a concomitant mild metabolic acidosis. During periods of renal dysfunction, the patients with DC developed severe hyperchloremic acidosis. Use of DC for pancreatic exocrine diversion may require patients to take supplemental bicarbonate even with a well-functioning renal transplant.