An 8-month-old boy with persistent watery diarrhoea and failure to thrive developed abdominal distension, hypokalaemia, and flushing of the face and trunk. A high concentration of vasoactive intestinal peptide-like immunoreactivity was found in the serum. Soon after resection of a suprarenal mass, the serum level of vasoactive intestinal peptide became normal and the diarrhoea stopped. Histologically the tumour was a ganglioneuroblastoma: the cells showed fluorescence by the indirect immunofluorescence technique with anti-vasoactive intestinal peptide serum. Electron microscopical examination showed abundant secretory granules in the tumour cells. Reports of chronic watery diarrhoea in children due to neural crest tumours are reviewed, with particular respect to the clinical features of the syndrome.