Investigators have previously reported good retention, antifertility efficacy, and oviduct polymer compatibility in rabbit oviducts in studies of both short-term and chronic occlusion with high viscosity silicone polymer. The present study attempts to determine the chronic effects of the silicone polymer installed into the oviducts of 10 rhesus monkeys. Unlike former studies with rabbits, the polymer was installed into the fimbrial end of the monkey's oviducts because of the complexity of the uterotubal junction's musculature. Studies with light and scanning electron microscopy were conducted to examine tissue reaction to plug retention. Despite our major modification of the installation technique, we obtained a retention rate of 50%. In addition, there was no evidence of inflammation or tissue distortion, and the polymer plugs were not affected by menstrual bleeding.