OBJECTIVE The purpose of the study is to evaluate the causative organisms, treatment methods, and visual acuity outcomes of patients treated for delayed-onset endophthalmitis associated with conjunctival filtering blebs. METHODS The medical records of 32 patients with conjunctival filtering bleb-associated endophthalmitis treated at the Bascom Palmer Eye Institute between 1989 and 1995 were reviewed retrospectively. Bleb-associated endophthalmitis was diagnosed at 1 month or more after surgery in all patients. Patients with bleb infections only but without, signs of intraocular infection were excluded from this series. RESULTS Previous antimetabolite therapy was used in 20 patients, including mitomycin C in 14 and 5-fluorouracil in 6. Streptococcal species were the most frequently cultured organisms occurring in 15 (47%) of 32 eyes. Of the 32 patients, 30 received intraocular antibiotics. The initial treatment included a pars plana vitrectomy in 18 patients and a vitreous tap without vitrectomy in 12 patients. Two of three patients who presented with no light perception vision were treated by evisceration. Overall, 15 (47%) of 32 patients achieved a final visual acuity of 20/400 or better. Of those patients with Streptococcal species cultured from the eye, 6 (40%) of 15 had a visual acuity of 20/400 or better compared to 9 (52%) of 17 in patients with non-Streptococcal species. CONCLUSIONS Delayed-onset endophthalmitis associated with conjunctival filtering blebs is a current and future concern, especially with increasing use of mitomycin C. The Streptococcal species are a common causative organism. Despite current treatment of these patients, the visual acuity outcomes generally are worse than in patients with acute-onset endophthalmitis after cataract surgery.