We experienced a case of early recurrence of pancreatic mucinous cystadenoma due to incomplete resection of the adjacent normal tissues of the lesion, which was classified into megacystic type and was successfully re-resected. The patient was a 47-year-old woman. In May, 1992, she was operated on for a giant cystic tumor of the pancreatic tail at another hospital. The resected specimen was 31×26×15cm in size. The microscopical diagnosis of the tumor was mucinous cystadenoma. Abdominal CT scan 3 months after the surgery revealed a cystic tumor in the pancreatic body and tail. The cystic tumor was growing to multiloculated cysts with the size of 7×9cm 1 year after the surgery. The patient was admitted to the hospital. The tumor was diagnosed as recurrent cystadenoma with malignancy. Resection of the pancreatic tail and body with splenectomy, partial colectomy and lymphnode dissection was carried out in May, 1994. The resected tumor was multiloculated cyst with clear mucinous fluid, and 10×8×6cm in size. The microscopical diagnosis of the tumor was mucinous cystadenoma without malignancy. The patient is well now free from the tumor recurrence 1 year 8 months after the surgery.