Beijing Silicon Rubber IUD was designed by Xuan Wu Hospital and Beijing Silicon Rubber Manufacturing Research Institute in 1980. Animal experiments of the silicon rubber were done, and toxic effect studied before clinical use. 1136 cases were reported at the end of 12 months by 6 hospitals in Beijing. The followup rate was 93.75%. Life table of 12 months showed the cumulative continuation rate of the IUD was 82.45%, pregnancy rate 4.5%, expulsion rate 8.49%, removal for medical cause 3.9%, and removal for personal reasons 0.64%. Among the side effects, menstrual irregularity was 5.03%, blood discharge 6.35%, dysmenorrhea 11.95%, backache 31.1%, and leucorrhea 18.12%. Menstrual blood loss was measured in 30 cases before and after 1, 2, 3 months of insertion. The mean blood loss before insertion was 51.96 ml (51.71 +or- 15.95), while 1 month after insertion it was 62.9 ml (70.59 +or- 26.81), 2 months after insertion 71 ml, and 3 months after insertion 75 ml. The morphological endometrial change as compared with that by induced stainless steel ring is not much heavier especially in regard to glandular and stromal changes. The endometrial cytologic count of white cells of the IUD group (34 cases) in comparison with that of the control group (36 cases) was about twice as much in number. As Moyer reported, the endometrial cell count of IUD cases was about 6-10 times that of control cases. The authors consider that the cellular reaction of this IUD is not much greater than that of other types of IUDs.