<h2>Summary</h2> The second report in the literature and the first successfully treated case of spontaneous pseudocystoduodenocolostomy is p resented. An attempt has been made to clearly distinguish between spontaneous intraperitoneal rupture of pancreatic pseudocysts and spontaneous perforation into the gastrointestinal tract. Rupture presents as an acute abdominal catastrophe in a patient with a history of pancreatitis and should be treated by external drainage. In the past this complication has produced a mortality of 60 per cent. Perforation presents a picture of abdominal pain, fever, nausea and vomiting, and diarrhea. Treatment varies with the location of the communication, and the over-all mortality should be significantly less than 50 per cent.