A 40-year old man with Behçet's disease was admitted for severe decrease of visual acuity. Since 1987, he had suffered from oral aphtha, retinitis, erythema nodosum, genital ulcer and epididymitis. He was diagnosed as complete Behçet's disease and has been administered cyclosporin A (CYA) and colchicine (Col). Because of repeated ocular attacks and reduced visual acuity, CYA was increased from 3.49 mg/kg/day (220 mg/day) to 6.35 mg/kg/day (400 mg/day) and Col, 0.5 mg/day to 1.0 mg/day. 2 weeks later, he revealed fever, generalized myalgia, muscle weakness and general fatigue, accompanying marked elevation of creatine kinase (4962 IU/l). CYA was discontinued and Col was diminished to 0.5 mg/day. The myalgia disappeared in 4 days and general conditions including creatine kinase were normalized within 2 weeks. We concluded that CYA was highly suspected of the cause of myopathy considering his clinical course.