The VIP response to a 30 minute bicycle exercise test with a workload of 50% of VO2 max was investigated in young men before and after 5 days of continuous physical activities, almost total sleep deprivation and limited amounts of food. It was shown that plasma VIP increased during physical exercise lasting for more than 20 minutes with a workload of more than 50% of VO2 max. A further increase took place in the early recovery period to a maximum level 5-10 minutes after the exercise. This response to exercise is even stronger after prolonged strain. Glucose infusion during the exercise almost abolished the increase of plasma VIP.