One case of "early" post-trabeculectomy endophthalmitis and five eyes with "late" endophthalmitis three to nine years after glaucoma filtration surgery are presented. Differentiation of early versus late endophthalmitis is based on the time of onset and pathogenesis. Retrospective analysis of 1100 consecutive trabeculectomies revealed an incidence of less than 0.1% for early and 0.2% for late endophthalmitis. Medical and surgical approaches are discussed. The presumed importance of identifying posterior extension into the vitreous and performing a therapeutic vitrectomy is emphasized.