To evaluate the frequency of fibrovascular ingrowth (FVIG) at sclerotomy sites in vitrectomized eyes of diabetic patients with postoperative vitreous hemorrhage referred for ultrasound biomicroscopy (UBM). Retrospective observational case series. Twenty-six eyes of 23 diabetic patients with recurrent, nonclearing postoperative vitreous hemorrhage subsequent to pars plana vitrectomy (PPV) for proliferative diabetic retinopathy (PDR). Ultrasound biomicroscopy evaluation of all sclerotomy sites in patients referred for postoperative nonclearing or recurrent vitreous hemorrhage after PPV for PDR. Correlation with intraoperative findings was obtained in eyes undergoing revision of the vitrectomy. Eight eyes underwent repeat UBM after revision of the vitrectomy, and changes at previous sclerotomy sites were evaluated. Ultrasound biomicroscopy images at each sclerotomy site were classified into 3 categories: none (grade 0), minor (grade 1), and major (grade 2). The UBM characteristics of each category were defined by the examiner. Logistic regression analysis was performed to identify prognostic factors associated with development of FVIG in the study patients. Grade 1 or 2 FVIG was detected in 85% of cases, and grade 2 FVIG was identified in >/=1 sclerotomy site in 58% of cases. Grade 1 or 2 FVIG was detected in 56% of microvitrector sites, 41% of infusion sites, and 61% of light port sites. Ten patients underwent repeat vitrectomy because of recurrent nonclearing vitreous hemorrhage and UBM images showing FVIG. Inspection of the sclerotomy site confirmed the UBM findings in every case. Eight of these patients underwent follow-up UBM evaluation subsequent to the repeat vitrectomy. In 6 of the 8 patients, follow-up UBM showed no residual FVIG. Ultrasound biomicroscopy showed FVIG in a high proportion of eyes that experienced recurrent nonclearing vitreous hemorrhage after PPV for PDR. Ultrasound biomicroscopy is capable of detecting and characterizing FVIG at sclerotomy sites and may aid in reoperative planning.