Both short- and long-acting formulations of oxytetracycline are commonly used in veterinary medicine to treat animals infected with gram-negative and gram-positive bacteria, rickettsiae, mycoplasma, and chlamydiae. To compare pharmacokinetics of short- and long-acting oxytetracycline in chickens, injectable formulations from the same pharmaceutical company were administered to healthy 6-week-old broiler chickens in accordance to the labeled instructions. Fourteen chickens were separated into 2 groups: chickens in group A (n = 7) were administered the short-acting formulation (10 mg/kg IM q24h) for 4 consecutive days, whereas those in group B (n = 7) were treated with a single dose (20 mg/kg IM) of the long-acting formulation. Blood samples were collected into heparinized tubes before and at 0.25, 0.5, 1, 1.5, 2, 4, 6, 8, 10, and 24 hours after initial treatment. Thereafter, blood samples were taken every 24 hours up to 120 hours. Plasma concentrations of oxytetracycline were determined by competitive enzyme-linked immunoabsorbent assay, and pharmacokinetic parameters were obtained. Both formulations delivered therapeutic plasma concentrations of oxytetracycline for approximately 100% of their respective dosing intervals as recommended. However, considering the additional labor, patient stress, and mortalities associated with handling, in addition to rejection of the carcass due to tissue necrosis resulting from multiple injections, we recommend use of the long-acting instead of the short-acting injectable formulation in broiler chickens.