Achalasia is a motor disorder of the oesopagus characterized by decrease in ganglion cell density in Auerbach's plexus. The cause of the lesion is unknown. This is to repeat on the occurrence of autoimmune phenomena in patients with achalasia, in particular circulating antibodies against Auerbach's plexus and its possible meaning. IgG-antibodies against Auerbach's plexus were determined by standard indirect immunofluorescence. Antibodies to the cytoplasm of Auerbach's plexus were found in 37 of 58 patients with achalasia at variable stages of the disease (I-IV) with a disease duration ranging from 1 to 20 years but only in 4 out of 54 healthy controls (specificity 93%, sensitivity 64%, p < 0.0001), and in none of 12 patients with Hirschsprung's disease as well as 12 patients with cancer of oesophagus and only in one of 11 patients with peptic oesophagitis as well as in one of 13 patients with myasthenia gravis. The present observations suggest that autoimmunity to Auerbach's plexus plays a role in the pathogenesis of achalasia, the mechanism of action is unknown.