Experience with 131 pseudocysts of the pancreas in 112 patients has been analysed with a view to answering specific questions. Spontaneous regression was documented in 8 per cent. Complications occurred in 33-5 per cent of the pseudocysts, including obstruction of adjacent organs, rupture, haemorrhage and pancreatic ascites. In 14 pseudocysts, rupture into the gastrointestinal tract, the peritoneal cavity or the pleural cavity when unassociated with haemorrhage, had a mortality rate of 14 per cent. Sixteen patients with significant haemorrhage associated with a pseudocyst had a mortality rate of 61 per cent; early direct surgical control is advocated. Pancreatic ascites was associated with 14-5 per cent of the pseudocysts and had a 40 per cent recurrence rate, which can be greatly diminished when operative procedures are guided by pancreatography. The mortality rate for the surgical treatment of 97 uncomplicated pseudocysts was 6 per cent and the recurrence rate was 11 per cent. The prime cause of death was haemorrhage. Seven of the 131 pseudocysts were synchronous and 12 were metachronous. The actual figure is probably higher. Small cysts of the head of the pancreas, impalpable at operation but demonstrable by pancreatography, may be the cause of severe, continuing or recurrent symptoms.