2146 cases of IUD insertions after hospitalization for abortion at a hospital in Chile were studied. In 1514 cases the IUDs were inserted immediately after abortion, in 430 cases between 1-5 days after the operation, and in 202 cases between 5-40 days after. It is concluded that immediate or early insertion results in a somewhat lower retention rate, but offers the advantage of making it possible to treat a greater number of patients, many of whom would not return later to have the IUD inserted. The incidence of removal for medical causes was very low and immediate insertion was found to be harmless. The medical causes of removal were the usual ones of bleeding, pain, and infection; the most frequent cause of interruption of use was expulsion, which tends to occur during the 1st few months of use and among younger women. The probability of failure due to pregnancy was somewhat higher than in the case of insertion during the intermenstrual period. Cases of voluntary removal tend to increase after prolonged use, and a study to analyze the actual reasons for this fact is necessary.