Ganglion cysts are common leions that are most often found around the hands and feet. Gnaglia around the proximal tibiofibular joint usually occur within the synovial membrane, tendon sheath or peroneal nerve, but they rarely occur within muscle. We report here on a case of a 60-year-old man who complained of an asymptomatic deep seated mass in the proximal part of the right calf that he''d had for more than two years. On magnetic resonance imagin, the lesion appeared as a cystic lesion within the gastrocnemius muscle without communication with the knee joint. To the best of our knowledge, intramuscular ganglion cyst has never been reported in the Korean dermatologic literature.(Korean J Dermatol 2010;48(1):56~59)