A 41-year-old man experienced continuous convulsions, unconsciousness, and a high temperature. His laboratory findings revealed an increase in serum creatine phosphokinase, serum myoglobulin, and urinary myoglobulin levels. He had taken many psychotropic drugs as treatment for schizophrenia and was very dehydrated. Because a diagnosis of rhabdomyolysis was suspected, Tc-99m HMDP bone scintigraphy was performed. It showed diffusely increased soft tissue uptake in his shoulder girdles, vertebral area, psoas iliac muscles, and gluteofemoral muscles, leading to a diagnosis of rhabdomyolysis. Bone scintigraphy is useful in making an early diagnosis and evaluating the location and degree of muscle injury in rhabdomyolysis.