The histochemical observation of β-glucuronidase in 45 cases of uterine cancer was carried out in fresh frozen sections by Seligman's method, utilizing 6-bromo-2-naphthyl-β-D-glucuronide as the substrate. In squamous cell carcinomas of the cervix, moderate enzymatic activity was observed in the cancer cells. This activity was higher than that of normal squamous epithelium. In adenocarcinoma of the body and the cervix, intense enzymatic activity was observed in the cancer. This was stronger than that of normal endometrium. The enzymatic activity of adenocarcinoma were generally higher than that of squamous cell cancers. Enzymatic activity in the stroma of cancer tissue was mainly slight. There were no correlation between enzymatic activity and the clinical stage of cervical cancer, and correlation between the enzymatic activity of the cancer tissue and frequency of delivery.