Abstract Objective Spermatozoa transport into uterus and fallopian tubes is directed to the side of the dominant follicle and seems to be controlled by the ipsilateral ovary. The objective of this study was to evaluate the temperature in the fallopian tubes as well as the concentrations of estradiol and progesterone in the utero-ovarian veins draining the ipsilateral ovary and compare these to the contralateral side of the uterus. Study design A prospective clinical study. Setting Academic-assisted reproductive technology program. Subjects Temperature was measured in both oviducts of 10 patients each in the early phase as well as during the late follicular phase during the course of examination of tubal patency and function. Blood samples of the ovarian veins were obtained during hysterectomy in 10 premenopausal patients with regular menstrual cycles. Five of the women were in the early follicular phase and 5 were in the late follicular phase. Results Late follicular phase temperature as well as concentrations of estradiol and progesterone were significantly higher in the ipsilateral tube and the utero-ovarian veins draining the ipsilateral ovary as compared to the contralateral side. No such differences were found during the early follicular phase of the cycle. Conclusions These data support our view that the uterus and fallopian tubes during the late follicular phase immediately before ovulation are composed of two functional units with different functional properties acting as a peristaltic pump resulting in increased transport of spermatozoa into the oviduct ipsilateral to the ovary bearing the dominant follicle and that this effect is mediated in part by the utero-ovarian countercurrent system.