Purpose: To investigate whether there are alterations in the humoral immune system in patients with Behcet's disease (BD) with ocular involvement. Methods: Twenty-four BD patients with active uveitis and without any other manifestations of the disease were included in Group I-a. The same patients were reassessed during the convalescence period and assigned to Group I-c. Moreover, 24 age- and sex-matched healthy controls (Group II) were included in the study. Serum levels of immunoglobulin (Ig) A, IgM, complement (C)(3), C-4, interleukin (IL)-6, IL-8, and tumor necrosis factor-alpha (TNF-alpha) in Groups I-a, I-c, and 11 were measured and compared. Results: IgA, C-3, C-4, IL-6, IL-8, and TNF-alpha levels were higher in Group I-a than in Groups I-c and II. Conclusions: IgA-, C-3-, C-4-, IL6-, IL8-, and TNF-alpha-mediated mechanisms might be responsible for ocular lesions in BD.