The pharmacokinetic behaviour of amoxicillin/clavulanic acid (4:1) combination was studied after intravenous and intramuscular administration of single doses (25 mg/kg body weight) to 15 turkeys and 15 chickens. The objective was to determine whether there are differences between turkeys and chickens in the disposition kinetics of amoxicillin and clavulanic acid. The plasma concentrations-time data were analysed by compartmental pharmacokinetic and non-compartmental methods. The disposition curves for both drugs after intravenous administration were best described by a two-compartment open model in turkeys and chickens. The apparent volumes of distribution of amoxicillin and clavulanic acid were similar in the two species. The body clearances of amoxicillin and clavulanic acid in turkeys were significantly slower than in chickens. The elimination half-life of amoxicillin was similar in turkeys (1.12 +/-0.09 h) and chickens (1.03 +/-0.11 h) after intravenous administration, but that of clavulanic acid differed significantly (P<0.05) between turkeys (1.12 +/-0.03 h) and chickens (0.98 +/- 0.05 h). After intramuscular administration both drugs had a significantly longer half-life (P<0.05) in turkeys and chickens than that after the intravenous treatment. The bioavailability after the intramuscular injection was high and similar with both drugs, but higher values were obtained for chickens than turkeys.