Between 1985 and 1990, 340 eyes with rhegmatogenous retinal detachment (RRD) and severe (stage C3 or worse) proliferative vitreoretinopathy (PVR) were treated with vitrectomy and randomly selected to receive perfluoropropane gas or silicone oil; 183 eyes had undergone no prior vitrectomy (group 1), and 157 eyes had undergone prior vitrectomy with intraocular gas tamponade (group 2). No differences were found between eyes in the two groups in achieving visual acuity of 5/200 or better (44% vs. 39%), macular reattachment (78% vs. 77%), or complete retinal reattachment (67% for both groups). In group 1, 74 eyes achieved complete retinal reattachment after only one operation; 41 additional eyes achieved reattachment after a second surgical procedure. In group 2, these numbers were 74 and 26, respectively. Eyes treated successfully after more than one operation were less likely to regain a visual acuity of 5/200 or better than those successfully treated with one operation (P < 0.01). There was no difference in hypotony between groups, but keratopathy was more frequent in eyes in group 2 (P < 0.05). The results suggest that differences in outcomes between group 1 and group 2 eyes are not as great as previously believed.