We describe a case of rhabdomyolysis associating hypothyroidism. Hypothyroidism frequently leads to myalgias, muscle stiffness, cramps and sometimes elevated leves of muscle enzymes, but rhabdomyolysis is quite rate. This report describes a case of rhabdomyolysis associating hypothyroidism in a 19-year old man. Muscle enzyme levels were typical of rhabdomyolysis. Muscle biopsy and electromyograpic findings were compatible with hypothyroid myopathy. Muscle functions completely recovered with levothyroxine therapy. The present case represents rhabdomyolysis secondary to undiagnosed hypothyroidism in a developed stage which manifests itself with rhabdomyolysis.