The association of risk of developing Behqet's disease with the presence of HLA-B51 has been reported. In a group of 46 patients, HLA-B51 was present in 71% of the patient group as compared with 13% of the control group, and the BSl-positive patient group had a more frequent family history of the disease and more enhanced neutrophil chemotaxis 2. The etiology of Behqet's disease is unclear, and some viral and/or bacterial infections are thought to be etiological factors. Cooper et al 3 reported that increased risk of Behqet's disease was associated with tonsillectomy, a history of cold sores, large sibsip size, late birth order, travel to countries with high-incidence of the disease, and first sexual intercourse before 16 years of age, and these findings implied the association of this disease with infection during childhood or adolescence in a predisposed host. Young et al 4 suggested that Herpes simplex virus type 1 (HSV1) might be involved in the immunopathogenesis of Behqet's disease. A significantly impaired uptake of 3H-thymidine by CD4 cells confined to HSV1 antigens was found in patients with this disease, as compared with healthy HSV1 sero-positive patients. This finding suggests that the HSV1 genome might affect Tcell immunoregulation. However, treatment with acyclovir, which is of proven efficacy in the treatment of HSV1 infection, failed to alleviate the frequency and severity of orogenital ulceration or