We encountered two patients with acute pandysautonomia who subacutely exhibited extensive autonomic dysfunction after antecedent infections. Although these patients had been suffering from autonomic disturbance for several months, they both had a good clinical course after plasma exchange and intravenous immunoglobulin therapy. Thin-layer chromatography (TLC)-immunostaining did not demonstrate any antibodies against gangliosides, but immunoblot analysis showed antibodies against a neuroblastoma cell line, SH-SY5Y, in serum samples. Furthermore, ganglionic acetylcholine receptor autoantibodies were detected in one patient. These findings suggest that neuronal antibodies against the autonomic nervous system play an important role in the pathogenesis of acute pandysautonomia.