Cell preparations from the posterior eye cup of the eye cultured for 2 days exhibited accessory activity for T-cell responses to a mitogenic treatment and stimulatory activity in a mixed leukocyte reaction (MLR), two functions characteristic of dendritic cells (DC). These activities both partitioned with cells having a low buoyant density, another characteristic of DC. Immunomagnetic separations with monoclonal antibodies against lymphoid dendritic cell surface antigens revealed that the accessory activity of the low-density cells was entirely associated with a small population of cells positively selected by these antibodies. Immunofluorescent staining with these same antibodies also revealed a small subpopulation of low-density cells having the morphology of DC. On cryostat sections of eye tissue the positively-stained cells were localized in the choroid and were not observed within the sclera or the retina. Based on these results we conclude that there are functional DC in the choroid, and we speculate that they may have a significant role in the inflammatory process during posterior uveitis.