Levels and isoenzyme profiles of beta-hexosaminidase were compared in extracts from normal ovarian and ovarian epithelial tumors. The specific activities of beta-hexosaminidase were significantly (P less than 0.001) higher in malignant than in normal ovarian tissues. The enzyme levels of the tumors depended on their degree of differentiation. Well-differentiated tumors had activities in the normal range, while poorly differentiated ones had values higher than the normal mean +/- 2 SD. The moderately and moderately to poorly differentiated tumors had intermediate levels. DEAE-cellulose chromatography was used to resolve the isoenzyme of beta-hexosaminidase. Two major forms, beta-hexosaminidase A and beta-hexosaminidase B, were detected in all the preparations. In one tumor specimen, a component eluting slightly ahead of beta-hexosaminidase A was also detected. For quick separation, a batch-wise procedure using DEAE-cellulose was adapted. Proportions of the isoenzymes A and B separated by batch-wise procedure were similar to those obtained by column chromatography. Heat stability, optimum pH, acid stability and substrate specificity of the beta-hexomsaminidase isoenzymes from ovarian tissues were similar to those from other human sources. Isoenzymes from tumor extracts were more labile to heat and acid pH compared with those from normal source. Slight differences in the affinity for the substrate p-nitrophenyl-beta-N-acetyl-galactosaminidase between the isoenzymes from normal and malignant ovaries were noted.