Dear Editor, Implementing health and family planning programs is the most effective way for birth control. Intrauterine device (IUD) is an effective long-acting contraceptive mean.1 Considering little side effects and good compatibility of IUD to physiologic hormonal alterations occurring during breast feeding, the device is an acceptable contraceptive mean in nursing mothers.2In spite of its advantages, there are reports on side effects of IUD during breast-feeding.3,4 Considering these controversies, we decided to examine the side effects of IUD in breast feeding and non-breast feeding mothers.All women who attended our center between 1996 and 1998, for insertion of IUD (n=731), were enrolled into this study. Out of 731 women, 45.8% aged between 20 and 24 years (mean±SD: 27.8±6.6), and 40.1% had elementary education. Most of them were housewives and 61.7% were breast-feeding mothers. Pain (1.8%), early bleeding (1.1%) and symptoms of vasovagal shock (7%) were recorded as early side effects in breast feeding mothers. Vaginitis (43.7%), inter-menstrual spotting (23.4%), cervicitis (22.2%), menorrhagia (13.3%) and unwanted pregnancy (0.7%) was the late side effects.There was a significant correlation between IUD side effects, such as irregular menstruation bleeding (12.6%; p=0.023), menorrhagia (13.3%; p=0.001), hypermenorrhea (13.7%; p=0.001), and cervicitis (22.2%; p=0.005) with breast feeding. Stanback, et al, and Chen, et al, showed that nursing mothers in comparison with non-breast feeding mothers, suffered more from longer menstruation and irregular bleeding,4,5 Thonneau, et al, on the other hand, stressed that the amount of menstruation bleeding among breast feeding mothers was lower than non-breast feeding mothers.6 According to our findings, the frequency of IUD side effects in breast feeding period is comparable to those in non-beast feeding period which is a sign of IUD safety in breast feeding period.According to our findings, we therefore, suggest that IUD placement should be done with proper and careful screening. Altering of observation methods, screening, regular check-up of samples, proper managerial strategies and enforcement of educational programs are among suggestions of this research for improvement of IUD use during the breast feeding period.