A 58-year-old woman who had presented with intestinal pseudo-obstruction died 9 months later from rapidly progressive neurologic symptoms and autonomic insufficiency. Her gastric emptying had been markedly delayed and transit of markers had been slowed throughout the small bowel. A 5-hour manometric recording of the antrum and duodenum had shown absence of the normal interdigestive motor complex, which was replaced by irregular contractile activity of reduced amplitude. A small-cell carcinoma of the lung was found at autopsy. Pathologic study of the gut showed widespread degeneration of the myenteric plexus, which was infiltrated by plasma cells and lymphocytes and contained significantly reduced numbers of neurons. The extra-intestinal nervous system had neuronal loss and lymphocytic infiltrates in dorsal root ganglia. Thus, a gastrointestinal neuropathy causing intestinal pseudo-obstruction may be the presenting manifestation of a paraneoplastic syndrome associated with small-cell carcinoma.