From 1983 to 1986, silicone oil injections were used to treat 31 patients with retinal detachment (RD) and advanced proliferative vitreoretinopathy (PVR). In 19 eyes (61%), perisilicone proliferation (PSP) developed causing recurrent RDs in 15 eyes (49%). At an average of 5 weeks after surgery, PSP occurred and was characterized by extensive transparent preretinal membranes with denser focal areas. Microscopic examination of five preretinal membranes showed droplets of silicone oil and necrotic cells on the silicone side and glial or retinal pigment epithelial cells, or both, on the retinal side, often in layers separated by extracellular matrix. Silicone oil was present in periretinal membranes removed several months after the intraocular silicone had been evacuated indicating that silicone within cells may persist despite the removal of silicone. The use of silicone oil to provide tamponade in eyes with recurrent PVR is associated with a high incidence of periretinal proliferation that frequently leads to recurrent RD and visual failure.