A 61-year-old man with incomplete Behçet's disease was admitted to our hospital because of weakness and muscle pain in August 2001. The patient was diagnosed as having incomplete Behçet's disease because of oral aphtha, genital ulcer and uveitis. He had been administered with colchicine since December 1999. Cyclosporin was added in June 2000, because of repeated ocular attacks. In May 2001, he noticed weakness of proximal limb muscles. In three months, severe generalized muscle pain and numbness in his hands progressed. Laboratory findings showed elevation of muscular enzyme, serum creatinine, and hepatic transaminases. Electromyography and nerve conduction studies indicated myopathy and mild polyneuropathy, respectively. On diagnosis as drug induced neuromyopathy, colchicine administration was stopped. But, severe muscle pain continued. Thus, the cyclosporin dose was also reduced. Seven days later, weakness and muscle pain disappeared and laboratory findings markedly improved. These data indicate that the pathogenesis of neuromyopathy in this case was closely related to colchicine and cyclosporin. Caution will be needed in using these drugs for patients with Behçet's disease.