Several complications of advanced diabetic retinopathy can be treated surgically. Vitrectomy can clear media opacities, relieve traction on the retina, and makes adequate laser treatment of the retina possible. Removal of premacular vitreous may also improve diabetic macular edema. Instrumentation, understanding of the pathophysiology, surgical skills as well as supplementary pharmacotherapy have improved surgical results. Indications and timing for surgery have considerably changed in the past decades and the threshold for surgery has been continuously lowered, as vitrectomy became safer. The primary disease of the retinal microvasculature with capillary occlusion and retinal ischemia is still the limiting factor, responsible for disappointing functional results in anatomically successfully operated eyes.