During 1983, 823 first trimester therapeutic abortions were performed at the University Hospital of Trondheim, Norway. Of these patients, 229 had an IUD inserted at the end of the operative procedure. The remaining 594 patients served as controls. Microbiological samples were taken from the cervix and the urethra. No prophylactic antibiotic treatment was given. Compared to the group of patients not selecting an IUD as contraception, there was no increase in readmission frequency due to immediate postabortal IUD insertion. There were no positive cultures for N. gonorrhoeae, and the relative number of positive chlamydia cultures was the same in both groups. In the IUD group we did not find any increase in complications such as bleeding, pain, perforations or infections. During the first year of observation, 3 pregnancies occurred in the IUD group, giving a Pearl index of 1.3 pregnancies per year. Continuation rate after one year was 72.8%. We recommend immediate postabortal insertion of an IUD after first trimester abortion as a practical and safe procedure.