Two patients suffering from endometrial adenocarcinoma (endometrial type) showed hyperamylasemia. The elevated level of amylase in the serum dropped to the normal range after operation in case 1. Case 2 had a recurrent tumor and continued to have a high amylase concentration in the blood. Isozyme analysis of serum-amylase showed predominant patterns of the salivary type. Tumor homogenates contained only salivary type amylase. Immunohistochemical staining revealed localizations of amylase in these tumor tissues. So it was clear that the production and secretion of salivary type amylase caused hyperamylasemia. Further study was done immunohistochemically to find the incidence of amylase-productive endometrial adenocarcinoma (endometrial type). It was shown that 56% of these tumors had amylase in neoplastic cells. Well differentiated adenocarcinoma showed a high frequency of amylase-positive findings. It was suggested that amylase measurement would provide useful information in checking the recurrence and in monitoring the therapeutic effects of endometrial adenocarcinoma.