Abstract: To identify the clinical picture of Behcet’s disease in a large cohort of patients (6500) in Iran, over a period of 35 years, and compare them with other large series from around the world. Methods: Patients with Behcet’s disease from all over Iran were seen in the Behcet’s Disease Research Unit by a multidisciplinary team (rheumatologists, dermatologists, and ophthalmologists). Diagnosis was based on ‘expert opinion’. Data were collected on a standardized data sheet (105 items), and stored in an electronic database. Data were updated at each follow-up. Results: Male to female ratio was 1.22 : 1.00. The mean age at onset was 26 years  11.3. The frequency of symptoms were: oral aphthosis 97.3%, genital aphthosis 64.6%, skin manifestations 64.9% (pseudofolliculitis 54.5%, erythema nodosum 22.5%, other lesions 7%), pathergy phenomenon 52.5%, ophthalmologic manifestations 56.8% (anterior uveitis 41.2%, posterior uveitis 44.9%, retinal vasculitis 32.1%), joint manifestations 37.4% (arthralgia 17.2%, monoarticular arthritis 7.6%, oligoarthritis 16.8%, ankylosing spondylitis 2%), neurological manifestations 3.8% (central manifestations 3.5%, mononeuritis multiplex 0.3%), gastrointestinal manifestations 7.4%, vascular involvement 8.3% (phlebitis 5.7%, superficial phlebitis 2.2%, large vein thrombosis 1.1%, arterial thrombosis 0.154%, aneurysm 0.5%), epididymitis 4.7%, cardiac involvement 0.6%, and pulmonary involvement 0.9%. Sedimentation rate was normal in 46.5% of patients. Abnormal urine sediment was detected in 12.2%. HLA-B5 was present in 53.3% and HLA-B51 in 47.9% of patients. Conclusion: Behcet’s disease is mainly seen in young people. The most frequent symptoms are mucocutaneous, ocular and joint manifestations. Comparison with large series did not show major differences. Key words: Behcet’s disease, vasculitides.