With endometrial biopsy prior to insertion of IUD it is possible to detect about 25% of contraindications, especially endometritis, which is often present without any signs of genital infection. After observations on 290 patients the authors found that hysterosalpingography would still show anomalies gone undetected by normal biopsy. Such abnormalities as hydrosalpinx, cervical carcinoma, and uterine anomalies constitute definite contraindication to the use of IUD. After such assessment the authors were able to improve IUD retention on 280 insertions, obtaining a retention rate of 87% after 1 year of use. (Summary in ENG).