By using HE, histochemistry and immunohistochemistry stainings, 64 cases of mucinous tumors of ovaries including 24 benign, 29 borderline and 11 malignant cases were studied. The epithelial lining was divided into 4 types, namely: cervical, intermediate, gastric and intestinal types. According to the morphological and histochemical characteristics the intermediate type epithelium might be a transitional form between the cervical type and the gastric or intestinal metaplastic type. Argyrophil cells appeared only in the gastric or intestinal type epithelium, and malignant transformation was also to be detected in these 2 types. The constituents and amounts of mucin showed obvious difference among these four types of epithelium. The amount of neutral mucin was prominently decreased during the process of malignant transformation of the intestinal type epithelium and the expression of sulphomucin was also slightly predominant than the sialo-mucin's, but these changes were not noticed during the malignant change of gastric type epithelium.