Behcet's syndrome is a systemic illness of unknown etiology characterized by necrotising vasculitis originally described in Turkey. Typical manifestations include urogenital ulcerations, eye inflammation and migratory thrombophlebitis. An unusual course of this disease is described. A 56 year-old man was admitted to the hospital with fever, milk-glass opacities on chest x-ray, mucosal defects on the tongue and penis, hematuria and proteinuria with functional disorder of kidney. Chlamydia pneumoniae, CIK positivity and C 3 complement decrease were found. Antibiotics and antimycotic drugs have shown only slight improvement of pulmonary lesions. An excellent effect in all pathological findings was achieved after prednison administered in dosis of 1 mg/kg and later cyclophosphamide administration (Fig. 7, Ref. 12).