A patient with an amylase-producing serous cystadenocarcinoma of the ovary had elevated serum and urine amylase levels and high levels of amylase in pleural and ascitic fluids. Serum and urine amylase levels reflected both surgical removal of tumor mass and response to chemotherapy. Tumor homogenates had pronounced amylase activity. Salivary type amylase isozyme patterns were found in electrophoresis of samples from all sources. Ascites tumor cells were successfully cultured and salivary type amylase was found in the culture media throughout 5 passages. The tumor was classified by light microscopy as poorly differentiated serous cystadenocarcinoma. Ultrastructural studies on the tumor were consistent with that diagnosis. Amylase was detected in the cells of the tumor examined by the immunoperoxidase technique.