Five Rhesus monkeys underwent cataract extraction and intraocular lens implantation. The right eyes had extracapsular extraction, implantation of a Shearing J-loop posterior chamber lens, and primary posterior capsulotomy. The fellow eyes had extracapsular extraction, subtotal posterior capsulectomy, a limited anterior vitrectomy, and anterior chamber implantation of a modified J-loop Sinskey-style intraocular lens. One to two weeks postoperatively, we inoculated the anterior chamber of each eye with 10,000 Staphylococcus aureus organisms. After enucleating the eyes, we obtained anterior chamber and vitreous cultures and examined the gross pathologic specimen for vitreous clarity 72 hours after inoculation. Twenty percent of right eyes had infection of the vitreous cavity, whereas in the fellow eyes, 80% demonstrated vitreal infection by examination of the sectioned gross pathologic specimens. Sixty percent of the left eyes had positive vitreous cultures. These findings suggest that the posterior capsule acts as a barrier to prevent the spread of infection from the anterior chamber to the vitreous cavity in experimental, primate pseudophakia.