Abstract: Behcet's Disease (BD) is classified among the Vasculitides. It is characterized by mucocutaneous and ophthalmologic manifestations and seen mostly in the Northern Hemisphere and in countries along the silk road. The characteristics of BD are presented here in a nation wide analysis of 3443 patients in Iran over a 21 year period. There was a slight male preponderance M.F ratio 1.4:1 (53.3% male/46.7% female). The mean age of onset was 26.2 years. The frequency of symptoms was as follows: oral aphthosis 95.8%, genital aphthosis 64%, skin manifestations 73.6%, ophthalmic manifestation 57.8%, joint manifestations 39.9%. Rarer manifestation include vascular, gastro-intestinal. CNS, epididymitis, cardiac and pulmonary involvement. Laboratory abnormalities include pathergy phenomenon in 61.5%, HLA-B5 54.6%, HLA-B27 9.6% and a false positive reaction for syphilis 2%. 55.8% had a raised ESR and 6.7% urinary abnormalities. There are two nation-wide surveys of BD in the world - the Iran and Japan Surveys. Although some symptoms were reported more frequently in Japan, the clinical picture was grossly the same in both countries.