Pars plana vitrectomy (PPV) with silicone oil implantation (SOI) was performed for advanced proliferative diabetic retinopathy (PDR) in 110 eyes of 98 diabetic patients. In 77 eyes (70%) it was a primary SOI as part of the initial operation; in 33 eyes (30%) it was a secondary SOI in reoperations. Indications for SOI were traction retinal detachment of the posterior pole, combined traction and rhegmatogenous detachment, vitreous haemorrhage with florid vascularised fibrous proliferations, and recurrent vitreous haemorrhage after PPV. The patients were followed up for 24 to 72 months, with a mean of 53 months. At the end of follow-up, anatomical success was achieved in 63 eyes (57%), and functional success with visual acuity 0.01 and better in 35 eyes (32%). Functional failures were caused by retinal redetachment in 47 eyes (43%), by secondary glaucoma in 10 eyes (9%), retinal ischemia in 15 eyes (13%) and keratopathy in three eyes (3%). The functional success rate decreased with follow-up from 67% after six months to 50% by 60 months after SOI. Silicone oil bubble in the anterior chamber, rubeosis iridis, cataract, and glaucoma were the most frequent postoperative complications. PPV with SOI was highly effective in many serious complications of advanced PDR. Functional success was mostly lasting and markedly improved the quality of life of these patients.