The relationship between intrauterine device (IUD) use and the development of endometrial cancer was assessed in data from seven countries that were collected between 1979 and 1988 for a multinational hospital-based case-control study. Two hundred twenty-six cases of endometrial cancer were compared with 1,529 controls matched for age, hospital, and year of interview. No significant association between use of an IUD and risk of endometrial cancer was observed (OR = 0.74, 95% CI = 0.4-1.33). There were no trends in risk with respect to duration of use, time since first use, or ages at first or last use. No cases had used a copper IUD (OR = 0, 95% CI = 0-1.71). Although women over age 55 who had used an IUD were at significantly increased risk, this unexpected finding is based on small numbers of users and requires independent confirmation. These results, along with those from other studies, provide reassurance that risk of endometrial cancer is unlikely to be increased by use of an IUD.