Amoxicillin was given to two groups of eight chickens at a dose of 10 mg/kg of body weight, intravenously (i.v.) or orally. Plasma concentration was monitored serially for 24 h after each administration. Concentrations of amoxicillin were measured using high-performance liquid chromatography. Pharmacokinetic variables were calculated, using a two-compartment open model. The elimination half-life, and the mean residence time for plasma were 8.17 +/- 0.31 and 10.46 +/- 0.51 h, respectively, after i.v. administration and 9.16 +/- 0.60 and 12.26 +/- 0.81 h, respectively, after oral administration. After single oral administration, amoxicillin was rapidly absorbed, with Tmax, of 1.00 +/- 0.06 h. Maximum plasma concentration was 160.40 +/- 4.67 microg/ml and mean amoxicillin concentrations > 15 microg/ml persisted for 24 h. Oral bioavailability of amoxicillin was found to be 63.00 +/- 4.58%. The results indicate that a dosage of 10 mg/kg administered orally at 24 h intervals should be effective in treating a variety of systemic infections in poultry.