The mechanisms by which the eye maintains an immunosuppressive environment has been the subject of recent investigations. In this report we investigated the ability of resident ocular cells from the iris, choroid, and retina to inhibit lymphocyte responses in vitro. Our results demonstrate that single cell suspensions derived from iris and choroid to inhibit alloantigen induced lymphocyte proliferation. We show that this inhibition was mediated by soluble factors which are low (<10,000) and intermediate (10,000-30,000) molecular weight molecules. This capacity is limited to iris and choroid and is not demonstrable in cell preparations derived from the retina. We conclude from our studies that cells derived from iris and choroid are capable of regulating immune responses and suggest that these cells (or their soluble products) may play a role in the immunosuppressive environment of the eye.