The Family Planning Centre of the Department of Obstetrics and Gynecology, University of Debrecen having more than 45,000 IUD cases provided a unique opportunity to study and evaluate the incidence of rare clinical events associated with long-term IUD use. Keeping in mind to get statistically valid results of such rare events, I have selected ectopic pregnancy and cervical carcinoma as the main focus of my Ph.D thesis. Since the incidence of these two rare events is in a minimum of magnitude of thousandth, statistical evaluations are valid provided with large number of cases and longer observation period. This becomes an absolute condition especially in terms of premalignant and malignant pathologies of the cervix. To the best of my knowledge, results based on a single centre’s direct clinical observation with such a huge number of stringently followed-up cases for a long period of use has not been published yet. The number of patients at risk at the end of follow up period of 10 years (550-846) and the cumulative women months of use (180,000-492,000) was sufficient to conclude valid statistical results. On the sound basis of these fulfilled conditions, it is concluded that there is no statistically significant difference in the occurrence of ectopic pregnancy among medicated and non-medicated IUDs, in other words: duration of use of IUD does not play any role in generating ectopic pregnancy. Similar results have been concluded for cervical carcinoma as well: in case of premalignant and malignant cervical pathologies – also based on a long follow-up (10 years), a great number of cases (more then 17,000 IUD insertions) and a huge observation period (163,567-492,836) – there were no statistically significant differences between the non medicated and the copper containing devices. As such, it can be stated that on comparison to the non-medicated (Szontágh) IUDs, the copper-containing intrauterine contraceptive devices do not have either an increased or a decreased risk of cervical cancer. The observation of the two rare clinical events during IUD use and the evaluation of the results with ectopic pregnancy and cervical premalignancies and malignancies further strengthen the opinion that intrauterine contraceptive devices still remain one of the most effective and safe method of contraception to avoid unwanted pregnancies.