Reports of the use of intravitreal bevacizumab (Avastin, Genentech) for the reduction of neovascularization in proliferative diabetic retinopathy have demonstrated significant regression in the number of new vessels. Reducing the vascularity of neovascular fibrovascular tissue can potentially reduce bleeding intraoperatively and thus facilitate the vitrectomy procedure. The investigators chose to investigate the potential benefit of the use of preoperative bevacizumab in the management of these most complex cases.