A small fraction of pancreatic cysts are neoplastic rather than inflammatory in origin. Failure to recognize the true nature of a neoplastic cyst will lead to an incorrect treatment strategy. This is a report of eight patients whose cystic neoplasms were misdiagnosed and maltreated. Five of the eight tumors proved to be malignant. Five were drained by anastomosis to a viscus and one by aspiration; drainage was recommended for the other two. Treatment by drainage led to complications (persistent painful gastric ulcer, infection in the cysts), growth of new cysts, no cures, but missed opportunities to cure cancer. Three patients with no metastases at first operation had metastatic spread to the liver, omentum, or lungs at reoperation. In three of the five cases initially treated by cystenterostomy (including one cancer), subsequent resection was possible and probably curative. One cystadenocarcinoma was watched for 3 years before apparently curative resection. Guidelines based on serum and cyst amylase levels, morphologic appearance, angiography, pancreatography, and biopsy are given for the purpose of differentiating inflammatory cysts from neoplastic cysts of the pancreas. Confusion of these entities should not occur, but errors can often be corrected.