The frequency of HLA-B5 in 24 Israeli Behçet disease (BD) patients from various subpopulations was significantly greater than in 615 control individuals (P less than 0.003). The relative risk for a B5 carrier to develop BD was calculated to be 5.0. Six patients were offspring of consanguineous marriages, which is not unexpected in the populations studied. Five of the patients had only one HLA-B antigen, which in four cases was B5. Two of the latter were B5 homozygotes, indicating a possible greater susceptibility. This study confirms the reported association between BD and HLA-B5 in a populationnot previously investigated. Furthermore, these data support the suggestion that B5 is associated with BD in populations deriving from the Mediterranean Basin, the Middle East and Far East.