OBJECTIVE To investigate retrospectively the visual course for proliferative diabetic retinopathy after pars plana vitrectomy. METHODS From January 2002 to December 2004, we operated 209 eyes with proliferative diabetic retinopathy. For this study, we selected 28 eyes in which the visual acuity could be followed for 6 months or longer after the vitrectomy. RESULTS The mean time period for reaching the best visual acuity after vitrectomy was 14.7 +/- 12.0 months. Depending on the type of diabetic maculopathy, the ischemic type, deposit type, and cystoid macular edema type required a mean time of 16 approximately 19 months. For the diffuse edema type, the mean was 9 months. It is significant that vitrectomy with triamcinolone acetonide (TA) resulted in visual improvement earlier than vitrectmy without TA (p value = 0.03).