The antibody titer in serum to Streptococcus pyogenes L-form and Staphylococcus aureus L-form were determined by enzyme-linked immunosorbent assay in 28 patients with Behçet's disease, 31 patients with other uveitis (sarcoidosis: 10, Harada's disease: 5, tuberculosis: 4, rheumatoid arthritis: 4, lues: 2, juvenile rheumatoid arthritis: 2, herpes simplex: 2, trauma: 2) and 16 healthy normal controls. All L-forms were induced by the penicillin disk method. The antibody titer to Streptococcus pyogenes L-form in Behçet's disease was lower than that of other cases of uveitis and controls, and showed significant differences between controls, rheumatoid arthritis, sarcoidosis, tuberculosis and Harada's disease by the Student's t-test. The antibody titer to Staphylococcus aureus L-form in Behçet's disease showed no difference between controls and other cases of uveitis. In each uveitis and controls, and between active and inactive stages of all uveitis, there were no differences between titers. In Behçet's disease, antibody formation to Streptococcus pyogenes L-form may be specifically disturbed.