Six of eight obese men ate significantly less food during an intravenous infusion of the C-terminal octapeptide of cholecystokinin (CCK-8, 4 ng . kg-1 . min-1) than during a saline infusion in a double blind experimental paradigm. Subjects stopped eating sooner during CCK-8. CCK-8 did not change the rate of eating. No overt side effects were reported or observed. This is the first report of the satiety effect of CCK-8 in obese humans and it suggests that the therapeutic potential of CCK-8 for the treatment of obesity deserves investigation.