In the absence of reliable baseline data for normal neuron density in the intestine, the diagnosis of hypo- and hyperganglionosis is purely subjective. This study has established the normal neuron density by neuron counts in paraffin sections taken both transversely (transverse sections, TS) and longitudinally (longitudinally sections, LS) in relation to the long axis of normal postmortem jejunum, ileum, and colon from 21 children (aged 4 weeks to 10 years). Intestine from two adults (aged 16 and 42 years) and colon alone from a further six adults (aged 16 to 83 years) were also studied. The mean density values in childhood were for jejunum 3.6/mm (TS), 3.7/mm (LS); for ileum 4.3/mm (TS, LS); and for colon 7/mm (LS), 7.7/mm (TS). The proximal margins of surgically resected colons from six patients with Hirschsprung's disease and one patient with suspected isolated hypoganglionosis were also analyzed and the neuron densities compared with the established postmortem data. Neuron density values outside two standard deviations from the postmortem mean were shown to correlate with continuing pseudo-obstructive symptoms in these patients.