The pharmacokinetics of conventional and long-acting oxytetracycline (OTC) formulation were evaluated in sheep at a single dosage of 20 mg-kg(-1) body weight (bw). Conventional formulation was injected by intravenous (IV) route and long-acting formulation of oxytetracycline was administered by intramuscular (IM) route, Then blood samples were taken at 0.25, 0.5, 1, 2, 4, 8, 12, 24, 36, 48, 60, 72, 84 and 96 hours. Oxytetracycline analysis was performed by HPLC in plasma. The plasma drug concentration-time profile was characteristic of a two-compartment open model. Following IM administration, time to reach maximal plasma drug concentration was 2 hours and maximal plasma drug concentration was 5.13 +/-0.31 mug/ml. After IV and IM administration of oxytetracycline, the elimination times were 1.14 +/-1.13 and 18.92 +/-1.86 hours, respectively. Intramuscular bioavailability was found to be 73%. Also, AUC was found to be 106.24 +/-8.92 and 78.92 +/-5.07 mug- ml(-1) hours', respectively, IV and IM.