Serum interleukin-2 receptor levels were evaluated in 69 patients who had chronic bilateral uveitis and in 22 control subjects. Fifty-one of the 69 patients with uveitis had the ocular type of Behçet's disease and 18 had pars planitis (intermediate uveitis). The mean serum interleukin-2 receptor level was 412.6 +/- 94.6 U/ml for the control group, 465.0 +/- 96.6 U/ml for the patients with intermediate uveitis, and 810.9 +/- 369.3 U/ml for those with ocular Behçet's disease. The serum interleukin-2 receptor levels of patients with ocular Behçet's disease were significantly different from the levels of both the control and the intermediate uveitis groups (P < .001). The differences in serum levels of patients with intermediate uveitis and the levels of the control subjects were not statistically significant. Treatment of patients with ocular Behçet's disease for four to six weeks with either cyclosporine, methylprednisolone, or a combination of both, decreased the intraocular inflammation in nearly all cases. The influence of treatment on the level of serum interleukin-2 receptor, however, was variable.