Of 26 patients undergoing revision of genitourinary prostheses the surrounding reactive fibrous capsule was biopsied in 25 and the draining lymph nodes also were biopsied in 4. The prostheses included 16 inflatable and 14 flexible penile devices, and 10 artificial urinary sphincters. Tissue was examined by light and transmission electron microscopy. X-ray microanalysis was done on intracellular and extracellular foreign material from each specimen. Silicone was found in 18 of the 25 periprosthetic specimens and in all 4 lymph nodes. Foreign body granulomas were identified in 14 of these 29 specimens. Examination of new and explanted versions of each prosthesis by scanning electron microscopy revealed free particles of silicone or silicates on the surface of most devices. Pitting and microfissuring were seen on a few of the new devices and on nearly all of the used ones. Thus, genitourinary prostheses shed silicone particles that can be found in the fibrous capsule and draining lymph nodes.