The authors reviewed the medical records of 191 patients (232 eyes) who underwent closed vitrectomy for complications of diabetic retinopathy to evaluate the clinical picture of postvitrectomy hemorrhage (PVH). One hundred thirty-nine eyes (59.9%) had at least one episode of PVH (average, 1.5 per eye) that was variable in onset, not associated with a known cause in four fifths, with no noted source in two thirds, and severe in three fourths of the cases. Using logistic regression statistical analyses, the factors significantly associated with decreased incidence of PVH include older age of patient (P = 0.0004), long duration of surgery (P = 0.0002), and poor preoperative vision (P = 0.05). Of the 139 eyes with PVH, 65 (47%) had spontaneous clearing in an average of 11.3 weeks, 53 (38%) required repeat surgery, and 21 (15%) were inoperable, lost to follow-up, or refused reoperation. Postvitrectomy hemorrhage did not significantly influence the final visual outcome.