Thirty-six cases of late onset endophthalmitis in patients with filtering blebs are presented. Onset of endophthalmitis ranged from 4 months to 60 years after bleb formation. Possible contributing factors could be identified only in a minority of patients. Aqueous, vitreous or both were cultured in all cases. Eighty-three percent of eyes were culture positive. Streptococci were the most frequent causative organisms, isolated from 57% of culture positive eyes. Twenty-three percent of eyes grew Hemophilus influenzae. Only two cases were caused by staphylococci. In general, the visual outcome was poor, probably primarily due to the virulence of the infecting organisms. Endophthalmitis remains a risk even many years after creation of a filtering bleb. The microbiologic spectrum in this clinical setting is considerably different from that of recent postoperative endophthalmitis. Based on the bacteriology and clinical course of the patients presented, recommendations for management are discussed.