The authors report a case of Propionibacterium acnes endophthalmitis after intracapsular cataract extraction with implantation of an anterior chamber intraocular lens. The patient's chronic inflammation persisted for 5 years after cataract surgery despite treatment with pars plana vitrectomy, intraocular lens removal, topical and oral steroids, and topical fortified antibiotics. Fluctuations in the inflammation were paralleled by changes in the size and appearance of a white plaque on the posterior corneal surface. Anterior chamber tap cultures were positive for P. acnes after 8 days of incubation under anaerobic conditions. The inflammation was not controlled until the posterior corneal plaque, which was the presumed nidus of the chronic infection, was removed and the patient was treated with intravitreal and oral antibiotics.