Adamantiades-Behçet's disease is a universal disorder with varying prevalence, i.e. 80-370 patients per 100,000 inhabitants in Turkey, 2-30 patients per 100,000 inhabitants in the Asian continent and 0.1-7.5 patients per 100,000 inhabitants in Europe and the USA. Certain ethnic groups are mainly affected, while the prevalence of the disease seems to be strongly dependent on the geographic area of their residence. These data indicate environmental triggering of a genetically determined disorder. The disease usually occurs around the third decade of life, however, early and late onsets (first year of life to 72 years) have been reported. Juvenile onset disease rates from 7 to 44% in different ethnic groups; juvenile disease is less frequent, i.e. 2-21%. Both genders are equally affected. Familial occurrence has been reported in 1-18% of the patients, mostly of Turkish, Israeli and Korean origin, and is increased in patients with juvenile disease. Oral aphthous ulcers represent the onset sign in the majority of patients worldwide (47-86%). Oral aphthous ulcers (92-100%), genital ulcerations (57-93%), skin lesions (38-99%), ocular lesions (29-100%) and arthropathy (16-84%) are the most frequent clinical features; sterile pustules (28-66%) and erythema nodosum (15-78%) are the most common encountered skin lesions. The positivity of pathergy test varies widely in different populations (6-71%). HLA-B51 is associated with high relative risk for the disease in a small geographic area of the Mediterranean Sea countries and Southern Asia. Diagnosis can be established 2 to 15 years after the onset of the disease. Male gender, early development of the disease, and HLA-B51 positivity are markers of severe prognosis (mortality rates of 0-6%).