PIP: 635 women with stainless steel rings retained in utero for 20 years or more and 724 women of similar age without IUDs as controls were under investigation. Comparison of incidences of clinical symptoms of paired wearers and controls by age in premenopausal women and by postmenopausal duration in postmenopausal women showed that the tinged vaginal discharge in the study group was 4.87% higher than the controls (P0.05). There was no difference in menorrhagia, irregular bleeding, or other main effects. No cancerous changes were found in the uterine curettage specimens of 374 IUD users in the study group. Special attention was paid to the epithelium at the site in contact with the IUD and its adjacent areas showed no apparent dysplasia. There were 9 cases (2.41%) with mild hyperplasia of the endometrium. The incidence had no correlation with the prolongation of insertion duration. Among the 315 relatively intact endometrium specimens, there were 32 cases of inflammation (10.15%). The incidence had no correlation with duration. 3 endometritis cases were actinomyces infection. Among 374 removals, the removal difficulties did not apparently relate with their IUD insertion duration but did correlate to duration of menopause. Hysterograms of 23 cases showed that atrophy of uterine cavities progressed with the increase of menopausal years; the longer the duration, the deeper incarceration of the IUD. (author's)