Summary. A miniature Geiger—Müller probe was inserted into one ovary of 8 women undergoing hysterectomy. A control probe was inserted into the other ovary of 2 of the women. Krypton-85 in 0·15 m-NaCl was infused into the adjacent utero-ovarian vein and the radioactivity was registered for 5–14 min after the infusion. An increase of radioactivity was recorded in the ovary in 5 cases. In one of the women with 2 probes, no increase in radioactivity was observed in the control ovary. The results show a local transfer of gas from the ovarian branch of the uterine vein into the adjacent ovary, which may be due to a countercurrent exchange mechanism between the vessels of the human uterine adnexa.