The plasma pharmacokinetic profile of recombinant porcine growth hormone (rpGH) was studied in six healthy gilts after a rapid single i.v. injection of 250 µg/kg rpGH. The linear pharmacokinetic properties of rpGH were investigated by giving four different doses of the hormone at intervals of 2 days. The plasma rpGH concentration was determined by radioimmunoassay with a lowest detection limit of 50 pg/ml. Plasma levels of rpGH were fitted to a three-compartment open model; a triexponential decrease in plasma rpGH with a rather long mean terminal half-life of 40.22 ± 5.623 min was obtained in these pigs. Linear pharmacokinetic properties of rpGH were confirmed in the additional pig that received doses between 25 and 250 µg/kg rpGH. The small volume of distribution, 0.029 ± 0.003 1/kg, indicated that most of the injected rpGH was confined to the blood and probably lymph. The total plasma clearance of rpGH was 31.80 ± 2.802 ml/h × kg. The results not only contribute significantly to our knowledge about rpGH pharmacokinetics, but also to future studies for the rational design of optimal dosage regimens and the development of a controlled-release device for