Specimens from the conjunctival sacs of 92 healthy eyes were cultured on 2 separate occasions to determine the presence or absence of a persistent anaerobic flora. Aerobic bacteria and fungi were also studied for comparison. Of the 184 eye cultures, 112 (60.9%) contained at least 1 microorganism. Obligate anaerobes were recovered from 51.6% (95/184) of the cultures. Propionibacterium acnes, the predominant anaerobe encountered, was present in 49.5% (91/184) of the eyes. Aerobic and facultatively anaerobic bacteria, present in 32.6% of the total eye cultures, were less common than obligate anaerobes. Staphylococcus epidermidis was the most common of these. Fungi were rarely found. The findings suggest that the conjunctival sac is sterile or normally contains small numbers of anaerobic, aerobic or facultatively anaerobic bacteria. As previously suggested, the origin of the bacteria in the eyes may be the skin of the eyelids.