The history of intra-uterine contraceptive device (IUCD) reaches back over several decades. However it was not until 1920`s when German physicians began to use this device as the method for the prevention of pregnancy. Although there were variable responses on this method, the effectiveness of such device for contraception was well recognized. The main reason against its use was a fear for the complications which might arise after the application. Inflammation, perforation and even carcinomas were feared. Up until 1950`s only sporadic interests on this matter appeared in the medical field. With the problems of rocketing population increase, a demand for a safe, easily applicable and effective contraceptive method became very acute. The field of intra-uterine contraceptive device investigation was encouragingly enlightened by the publications of Oppenheimer and Ishihama in 1959 who reported much favorable results on the safety and effectiveness of this method. Following this, many pertinent data have accumulated in the world medical literature concerning IUCD and in many parts of the world the polyethylene loop insertion has been accepted as the method of choice. This immediately forces us to assay its hazards very care fully. It is true that there have been sporadic reports on the bacteriologic and histologic effects of such device, however, these reports are in many ways contradictory and fragmentary. Particulary there have been no reports dealing with the histochemical changes of the endometrial tissues in these situation. Furthermore, it is not yet clearly known how this device is so effective in preventing pregnancy. It is the purpose of this paper to descrive the clinical and histological effects on the endometrial tissues which might be related to insertion of IUCD and to characterize the histochemical changes so produced.