The present studies were carried out to clarify the indigenous bacterial flora in the female internal genitalia and surrounding tissues and the pathogenesis of parametritis. Twenty nine patients with uterine tumors which consisted of sixteen carcinomas and thirteen benign tumors underwent abdominal total hysterectomies. Each tissue aseptically collected from the uterus and adnexae was cultured for 48 hours under aerobic or anaerobic conditions and the bacterial species were isolated and identified. In benign uterine tumors, anaerobic bacteria were isolated in six patients and aerobic or anaerobic bacteria were identified In the endometrium, fallopian tube and parametrium of five of the patients. In a group of carcinoma in situ (stage 0), many bacteria were isolated in two patients after conization. In the uterine carcinomas, as the stage advanced, the rate of bacterial isolation from parametrium and lymph node became higher. The rate of anaerobic bacterial isolation, except for one from the vagina, was nine out of sixteen patients with carcinomas but three out of thirteen patients with benign tumors. The results revealed that the bacterial flora in the vagina spread to the internal genital organ and surrounding tissues via the ascending or cervical lymphatic pathway and remained there as nonpathologically indigenous bacterial flora. These results suggest that these indigenous bacterial flora in the internal genitalia and the surrounding tissue may cause an opportunistic infection.