Five cases of Guillain-Barré' syndrome treated with ACTH or Cortisone are reported. Rapid improvement of the symptoms occurred in all cases. The time of evolution in these cases was shorter than that commonly observed when the disease was not submitted to this therapy. The shortening of the evolution when the disease is treated with ACTH or Cortisone supports the allergic theory on its pathogeny, as well as its inclusion among the demyelinating diseases of nervous system.