Abstract
1. Plasma VIP immunoreactivity is always diagnostically raised in patients with pancreatic tumour causing the Verner-Morrison syndrome. 2. Human tumour VIP is physico-chemically similar to porcine VIP. 3. The only other situation in which plasma VIP is very elevated is in patients with ganglioneuroblastomas associated with diarrhoea. 4. VIP is not elevated in patients with diarrhoea associated with pancreatic islet hyperplasia, designated the pseudo Verner-Morrison syndrome.