It is well known that patients with Behçet's disease (BD) have an activated immune system, probably mediated by soluble factors in the circulation. The purpose of our study was to examine the roles of plasma interleukin-2 (IL-2) and soluble interleukin-2 receptor (sIL-2R) in the pathogenesis of BD. Thirty-two patients with BD diagnosed according to the Criteria of the International Study Group for Behçet's Disease and 20 age-matched healthy persons were included in the study. The plasma levels of cytokines were measured by ELISA. Plasma levels of IL-2 and sIL-2R were increased in BD over controls, but the differences were not statistically significant. sIL-2R levels in patients with active disease were significantly higher than in either patients with inactive disease (p < 0.001) or the control group (p < 0.05). Our results suggest that the level of sIL-2R in BD seems to be related to disease activity.