PIP: Results of tests based on the hypothesis that sustained release of an antifibrolytic agent from an IUD may control the bleeding complications associated with IUD contraception are reported. Devices releasing epsilon aminocaproic acid (EACA) were made from silicone rubber encased in nylon-baked millipore tubes. These devices were cylindrical with a diameter of 1.9 mm and lengths of 14 mm. For easy removal a central core of stainless steel extended beyond 1 end to form a closed loop. Menstrual blood loss (MBI) in a group of Rhesus monkeys was quantitated before and after insertion of a nonmedicated silicone device, a standard polyethylene device, or medicated silicone devices. A beneficial effect of medication with EACA was demonstrated. With nonmedicated silicone devices MBL increased 96% over preinsertion values. EACA-releasing devices caused only a 33% increase during the first menstrual period after insertion. Mean MBL was increased 109% in animals wearing polyethylene IUDs alone and 132% in those wearing polyethylene plus control silicone devices. MBL was increased only 44% in monkeys wearing polyethylene plus EACA medicated silicone devices. In animals with EACA devices no local or disseminated intravascular coagulation was detectable by assay of circulating levels of fibrinogen, plasminogen, or fibrin-fibrinogen degradation products. Although the effects of EACA occurred at a high intrauterine dose for only 1 menstrual period, a much smaller dose might be effective. Studies are being made to fabricate a device that would last for 1 year or more in humans. Complete inhibition of fibrinolytic activity in the uterus at the time of menstruation would be harmful so it is not sought.