PIP: Sperm transport was characterized on optimal, controlled, assessable conditions in this study. Subjects were women who had requested surgical sterilization. All subjects were restricted from coitus for 11-14 days preoperatively. The study was performed within 36 hours of the estradiol preovulatory peak for each subject; so surgical excision of both fallopian tubes was accomplished at predetermined times after insemination with fresh, whole, high-quality ejaculates; the cervical mucus column was also removed. Using this technique, sperms were identified in the oviduct within 5 minutes from deposition in the proximal vagina. Numbers of sperm in the oviduct were directly related to numbers inseminated. Sperm distribution was throughout the oviduct and was highest in fimbria (tubes had been divided in thirds upon excision). For 15-45 minutes after insemination, a constant level of sperm existed in the oviduct. 1 subject was studied similarly to determine the presence of sperm in endometrium, and no sperm occurred in that cavity until 80 minutes after insemination. This study also reports the total numbers of sperm present in cervical mucus and the correlation of insemination and time after insemination.