Internal pancreatic fistulae are well-recognized complications of inflammatory pancreatic disease. From 1963 to 1990, 50 patients with either pancreatic ascites (34), pancreatic ascites and pleural effusion (7), or pancreatic pleural effusion (9) were treated. Initial therapy was conservative, consisting of gastrointestinal rest, serosal apposition with paracentesis or thoracentesis, with or without the administration of anti-secretagogues. This therapy was successful in 21 of 42 patients, but 5 deaths occurred. Operative therapy was performed in 24 patients. There was one surgical failure and two deaths early in the experience. Ten of our final 16 patients underwent liver biopsy, and all 10 were found to have cirrhosis. All patients, even those with documented cirrhosis, should have routine amylase and albumin determinations on ascitic or pleural fluid. Internal pancreatic fistulae should be treated initially nonoperatively; if this is ineffective, operative therapy has an acceptably low morbidity and mortality.