To know the prognosis of Behçet's disease with HLA-Bw 51 antigen, comparison studies of 24 cases of Behçet's disease were investigated. The sex distribution was 14 males (58%) and 10 females (42%). The patients were grouped into three clinical types: the complete type with 11 cases (45%), the incomplete type with eight cases (33%) and the suspect type with five cases (22%), according to the criteria established by the Behçet's Disease Research Committee in Japan (1982). They were also divided into three ocular types according to the location of the inflammation: the anterior segment type, the fundus type and the mixed type. They were divided into 10%, 10% and 60% in HLA-Bw 51 negative group and 14%, 22% and 64% in HLA-Bw 51 positive group, respectively. Skin lesions observed in 30% of the HLA-Bw 51 negative group and 70% of the HLA-Bw 51 positive group, which was statistically significant (p less than 0.01). The other general symptoms and the visual acuity between the two groups were not statistically significant (p greater than 0.1).