Abstract
A specific radioimmunoassay has been developed capable of detecting 1.5 pmol VIP/l plasma with 95% confidence. The antisera employed reacted most avidly with whole VIP, partly with C terminal, but not with N terminal fragments. In 110 healthy fasting volunteers plasma VIP concentrations were estimated to lie between 0.5 and 21 pmol/l (median 1.7). No significant change was seen after ingestion of a standard test meal.