The authors studied one case with rhabdomyolysis associated with acute renal failure, which followed acute CO intoxication. Oliguria, hyperkalemia developed within one day of rhabdomyolysis on left extremities. During the first three days of hospitalization, rapid increase in serum BUN, serum creatinine and serum muscle enzymes (CPK, LDH, GPT, GOT) were noted. Renal failure was controlled by artifiral kidney. Several areas of increased uptake of technetium-99m DP were noticed on bone scan. Electron microscopic examinations of biopsied muscle consist of disarrangement of myofibrils, loss or destruction of Z-line, difficulties in distinguishing A-band from I-band, and swelling of mitochondrias. These findings suggest that acute CO poising may be followed by severe muscle destruction and renal damage.