We examined the vitreous in 163 eyes with diabetic retinopathy using a +58.6-diopter aspherical preset lens and a slitlamp. Sixty-eight eyes had no vitreous detachment, 76 eyes had partial vitreous detachment, and 19 eyes had complete vitreous detachment. This article studies the vitreoretinal relationship to determine its role in the progression of proliferative diabetic retinopathy. We found that partial vitreous detachment with vitreoretinal traction is a major risk factor for progression of proliferative diabetic retinopathy, whether or not photocoagulation is performed. With complete vitreous detachment or with no vitreous detachment, the absence of vitreous traction protects against the progression of proliferative diabetic retinopathy.