AIM:To evaluate the effect of intravitreal bevacizumab (IVB) injection 1 week before pars plana vitrectomy (PPV) in proliferative diabetic retinopathy (PDR) patients. ·METHODS:A retrospective research was done on 46 PDR patients who were divided into PPV group (n=28) and IVB group (n=18,PPV with preoperative IVB). Bevacizumab was injected 1 week before PPV. Main outcome measures were visual acuity,incidence of iatrogenic retinal breaks,intraoperative and postoperative bleeding. ·RESULTS:At 1 month after surgery,visual acuity in PPV (82.1%) and IVB group (88.9%) improved significantly (P<0.01) and the difference between the two groups was not significant. Iatrogenic retinal breaks were reported in 18 cases (64.3%) in PPV group and 4 cases (22.2%) in IVB group (P<0.05). Intraoperative bleeding was encountered in all cases in PPV group and 7 cases (39%) in IVB group (P<0.01). Postoperative bleeding was reported in 9 cases (32.1%) in PPV group and none in IVB group (P<0.01). ·CONCLUSION:IVB injection before PPV is helpful in reducing iatrogenic retinal breaks,intraoperative and postoperative bleeding in PDR patients.