The pharmacokinetics of sulphaquinoxaline and amprolium hydrochloride were studied in Hubbard broiler chickens. Single doses of sulphaquinoxaline (100 mg/kg b. wt.), and amprolium hydrochloride (30 mg/kg b. wt.) were administered orally and intravenously to the same birds with 15 days interval between treatments. Sulphaquinoxaline and amprolium HCl were determined colorimetrically. Following i.v. administration, the concentration-time curve of sulphaquinoxaline and amprolium could be explained by a two compartments open model with a t1/2 alpha of 0.16 +/- 0.008 h; 0.17 +/- 0.09 h; t1/2 beta of 12.6 +/- 0.32 h, 4.89 +/- 0.3 h respectively. The total body clearance were 0.278 +/- 0.013 ml/kg/min; 0.562 +/- 0.015 ml/kg/min; volume of distribution at steady state were 0.44 +/- 0.009 L/kg, 0.34 +/- 0.005 L/kg and systemic bioavailability following oral administration were 72.65 +/- 3.38, 66.09 +/- 4.9 percent for sulphaquinoxaline and amprolium HCl respectively. Following oral administration of sulphaquinoxaline and amprolium (the same previous doses) the peak plasma concentrations (Cmax) were 107.8 +/- 1.49 micrograms/ml; 42.9 +/- 1.11 micrograms/ml and occurred at 5.56 +/- 0.1 h, 3.67 +/- 0.05 h respectively. Pharmacokinetic parameters after repeated oral daily administrations of sulphaquinoxaline and amprolium revealed that the Cmax was 184 +/- 1.02 micrograms/ml, and 55.19 +/- 0.35 micrograms/ml at 7.36 +/- 0.18 h and 5.17 +/- 0.15 h and the biological half lives were 1.67 +/- 0.057 h and 1.11 +/- 0.14 h respectively. Sulphaquinoxaline and its N4 acetyl metabolite disappeared from all body tissues at 120 hours, however amprolium persisted in most tissues for 72 hours after the last dose of repeated administrations.