Clinical follow-ups of 235 patients following vitrectomy and silicone oil injection were evaluated with special regard to the occurrence and time course of reproliferations. The total incidence of reproliferations was 33%. The highest rate was found after ocular injuries (47%), followed by rhegmatogenous retinal detachment (30%) and proliferative diabetic retinopathy (23%). In all three groups the incidence of reproliferation was highest during the first three postoperative months. In cases with ocular injuries and rhegmatogenous retinal detachment, the rate of reproliferation was found to be highest during the first postoperative month, while in cases of proliferative diabetic retinopathy the incidence peaked during the second and third months. Therefore, in order to prevent complications due to the silicone oil, the oil should be evacuated between the third and sixth postoperative month.