Forty-five patients with pancreatic cystadenoma were treated surgically at the Mayo Clinic between 1939 and 1975. Each lesion was classified as mucous or serous. The most frequent lesion site was the tail of the pancreas. The typical patient was a middle-aged woman with upper abdominal pain and a palpable mass on initial examination. Total extirpation of the cystadenoma was the treatment of choice; internal drainage or external drainage of these cysts should not be done. Occasionally, the nearness of the tumors to the mesenteric vessels precluded excision. The mucous type had malignant potential whereas the serous does not. None of the cystadenomas subsequently underwent malignant degeneration. Because of the slow-growing characteristics of the tumor, undue operative risks should not be taken.