In a retrospective study of 12 patients with Behçet's disease, more than half were found to originate from the Near East, where the prevalence of the disease is known to be high. The immigrant patients were all males, whereas 3 of the 5 patients with Swedish ancestry were females. Certain differences emerged between the two groups, including different sex ratio and absence of HLA B5 association and pathergy skin reaction among the Swedish patients. Moreover, serious neurological and ocular symptoms showing no tendency to recede with age afflicted all the Swedish female patients. Urogenital symptoms were, besides ulcers, common in both groups, including prostatitis, urethritis, orchitis, chronic sterile cystitis and relapsing salpingitis. Although the maternal does not allow statistical inferences, the estimated prevalence was higher than expected among both Swedish and immigrant patients. Recent studies, including the diagnostic criteria proposed by the "International Study Group for Behçet's disease", are discussed in relation to previously used criteria as well as present findings. The sensitivity and specificity of the first mentioned criteria and the ones proposed by Mason & Barnes seemed equal.