Peptide tyrosine-tyrosine (PYY) is a prandially controlled hormone in endocrine ileal and colonic mucosa cells. In plasma, PYY appears as full-length PYY1-36 and truncated PYY3-36. Both have different pharmacological profile, and PYY3-36 seems to inhibit food intake. We aimed at investigating the effect of intravenously administered PYY1-36 and PYY3-36 on gastric emptying and short-term metabolic control. Eight healthy adults were studied in single-blinded, randomized design. At separate occasions, intravenous infusion of saline, PYY1-36 or PYY3-36 (0.8 pmol kg(-1) min(-1)) and a radio-labelled omelette were given. Gastric emptying (scintigraphy), appetite ratings (VAS), and plasma concentrations of insulin, glucose, GLP-1 and PYY were measured. PYY3-36 and PYY1-36 both inhibited gastric emptying, PYY3-36 most effectively. Half-emptying time was prolonged from 63.1+/-5.2 (saline) to 87.0+/-11.5 min (PYY3-36), whereas retention at 120 min was 2.5+/-1.4% for saline, 10.7+/-4.4 for PYY1-36 and 15.8+/-4.4 for PYY3-36. Neither form influenced glucose or GLP-1 concentrations, but both decreased the postprandial rise in insulin. PYY3-36 induced nausea (VAS increase 47.5+/-22.6 mm) and decreased prospective consumption (VAS change 39.5+/-7.7 mm). In conclusion, PYY3-36's reducing effect upon food intake might be mediated by a decreased gastric emptying rate.