A 25-year-old female who had right knee and ankle joint swelling with arthralgia in July 1999, was diagnosed as having eosinophilic fasciitis (EF) based on typical skin sign and the result of muscle biopsy. Treatment was started with 20 mg of oral prednisolone per day. Her symptoms had subsided but they later recurred as the prednisolone dose was gradually tapered. We measured her serum cytokine levels during the course. Her serum IFN-gamma increased and IL-4 decreased after the treatment compared with those levels prior to treatment. And the cytokine levels reverted to pre-treatment status when she had a relapse. The cytokine balance seems to play some role in the etiology of EF.