Menstrual blood loss (MBL), haemoglobin and serum ferritin levels were studied in a total of 127 women from three developing country centres, using a vaginal ring releasing 20 μg levonorgestrel/day. The objective was to evaluate changes in MBL and body iron stores over one year of use. The discontinuation rate for bleeding problems varied between centres from 3 to 13% at one year, but these differences were not significant. There were no differences in MBL or iron status on admission between women who completed or discontinued from the study. Even though there was considerable variation in MBL and haemoglobin levels among the three centres before insertion of the ring, a decrease in MBL was observed in all centres after commencement of ring use. Conversely, an increase in haemoglobin levels was noted in all centres although the change reached significance only in Beijing. There were no alterations in serum ferritin levels. These results suggest that use of a vaginal ring releasing 20 μ