In the Silicone Study, 117 of 404 eyes (29%) with severe proliferative vitreoretinopathy (≥ C-3, full-thickness retinal folds in three or more quadrants) enrolled in the study were treated with vitrectomy, underwent a relaxing retinotomy, and were randomly assigned to treatment with long-acting gas or silicone oil. Forty-six eyes (20%) had undergone no previous vitrectomy (group 1); 71 eyes (42%) had undergone previous vitrectomy (group 2) with intraocular gas tamponade (P < .001). Group 1 eyes not undergoing retinotomy had better anatomic (six months) and visual (six and 24 months) outcomes and less hypotony (six months) than eyes that did regardless of tamponade (P < .05). For eyes undergoing retinotomy, silicone oil decreased the likelihood of hypotony (six months, P < .05). These differences were not found in group 2 eyes. We conclude that eyes undergoing a vitreous operation for the first time for the treatment of proliferative vitreoretinopathy can in most instances be successfully treated by conventional techniques without the need for relaxing retinotomy. Retinotomy may be required more often in patients undergoing repeat vitreous surgery for proliferative vitreoretinopathy, in which case both silicone oil and long-acting perflouropropane gas appear to be equally effective.