Although the research trends in studying Behçet’s disease (BD) were reviewed in this Journal in 2002, I would again like to introduce the articles from the point of view of the latest research results for BD pathogenesis, the newly revised diagnostic criteria, and the current treatments. The number of BD patients registered with the Japanese Ministry of Health, Labour and Welfare reached nearly 20,000. The sequence based tying of the HLA gene revealed that HLA-B51 and its HLA-B*510101 allele were significantly associated with BD immunopathogenesis as the intrinsic factor, suggesting that BD might be distributed from the Mediterranean countries to the Far East. Streptococcus (S.) sanguinis (old classification: S. sanguis), which is freguently isolated from the oral cavity of BD patients, is suspected to be one of the external factors triggering the BD symptoms in the pathogenesis, because BD patients have intense hypersensitive reactions to S. sanguinis related materials. The heat shock protein (HSP)-65 derived from S. sanguinis is found to cause human HSP-60 in the sera of patients who have some peptides homologous to HSP-65. Although it has been thought that these homologous regions may enhance the inflammation of BD lesions, it is suggested that some regions can reduce the production of inflammatory cytokines, such as IL-12, IL-6, IL-8, TNF-α, etc., from peripheral blood mononuclear cells (PBMC) of BD patients. It is found that these homologous regions were also homologous to the epitope of T cells of BD patients. Lehner and his research group, UK, have recently demonstrated that the clinical tolarization could be induced to the advanced uveitis of BD patients for treatment by use of the homologous peptides (p336–351) combined with choleratoxin B. Regarding to the immunological condition of BD patients, it has been cleared that cytotoxic T cells, CD3+, CD8+T cells and γδT cells including CD69+ cells, are accelerated in active disease stage of the patients and that they are stable in the remission. The newly revised diagnostic criteria (2003) which may be able to investigate the quality of life (QOL) and the prognosis of BD patients and the treatments for BD patients with various clinical types including biological treatments using anti-TNF-α and anti-IL-6 antibodies are introduced here.