A series of 354 consecutive rhegmatogenous retinal detachments, operated on by means of microsurgery, is evaluated to determine the clinical factors that may predispose to the development of postoperative massive proliferative vitreoretinopathy (MPVR). Three statistically significant parameters in the development of postoperative MPVR are demonstrated: failure of previous surgery, preoperative fixed retinal folds, and horseshoe retinal tear(s) exposing a total surface of 3 disc diameters or more of pigment epithelium. For further study, it is suggested that in retinal detachments with such horseshoe tears, early destruction of the exposed pigment epithelium by argon laser photocoagulation may be a valuable means of decreasing the incidence of MPVR after retinal detachment repair.