The acute inflammatory demyelinating polyneuropathy (Guillain-Barré Syndrome) might have a severe presentation but a good prognosis in children. It is an immune-mediated and inflammatory disorder of the peripheral nervous system. This retrospective study observed that GBS is frequently complicated by hypertension and other autonomic disorders. Cardiovascular instability is due to the involvement of the autonomic nervous system and results in labile blood pressure, cardiac dysrhythmias and hypovolemia. During a 13-year period (1982-1995), 21 children were admitted to the Pediatric Intensive Care Unit of São Lucas Hospital, Porto Alegre, south of Brazil. Eight patients were mechanically ventilated. Symptoms of autonomic disturbance were frequently seen, especially in patients with severe clinical evolution. Previous investigations of the mechanism of hypertension associated with GBS did not evaluate the etiology of these phenomena. With modern pediatric intensive care support the deaths are rare. There is no death in this studied group.