The pharmacokinetics of porcine glucose-dependent insulinotropic polypeptide were investigated in six healthy volunteers. At the maximum infusion dose (0 . 5 pmol kg-1 min-1) a plateau concentration of 115 +/- 5 . 0 pmol/l plasma was obtained. On discontinuation of the infusion, the half-time of disappearance was calculated to be 20 . 3 +/- 1 . 2 min. The metabolic clearance rate was 2 . 6 +/- 0 . 1 ml kg-1 min-1 and the apparent space of distribution was 75 . 8 +/- 5 . 7 ml kg-1. Blood glucose, pancreatic and gastrointestinal hormones remained at basal concentrations throughout. No side effects were noted by any of the subjects studied.