The histopathology of 40 cases of achalasia of the cardia, 6 cases of oesophageal spasm-incoordination and 4 cases of scleroderma was examined. Three cases of carcinoma and 6 cases of reflux oesophagitis were used as a control group. A nearly complete loss of myenteric ganglion cells was found in the upper thickened segment in achalasia. Some surviving ganglion cells were found in the lower segments in half the cases of achalasia; in two cases counts were normal in this segment. The occurrence of neuronal chromatolysis in 9 biopsies of achalasia supports the view that an active disease process was involved. The preganglionic parasympathetic fibres in two cases of achalasia were normal in appearance and number; this somewhat limited evidence tends to count against a primary disorder of the preganglionic neurone in this condition. The 6 cases of oesophageal spasm-incoordination showed similar neuronal loss to that in the lower segment in achalasia. Possibly "oesophageal spasm" represent an early stage or incomplete expression of achalasia. One cases of scleroderma showed loss of ganglion cells, but the myenteric plexus was here involved by the disease process. None of the 9 cases in the control group showed any loss of ganglion cells or chromatolysis. Acute and chronic inflammation was not convincingly associated with loss of ganglion cells in either achalasia or oesophageal spasm.