Tilmicosin is a long-acting macrolide antibiotic used in the treatment of respiratory disease. It was administered once (SO mg/kg b.wt) to fowls via the oral route for determination of kinetic properties and tissue levels. After oral administration, tilmicosin's pharmacokinetics conformed to a two compartment open model. Tilmicosin was slowly eliminated from the serum and lung with mean half-lives of 30.18 +/- 2.38 and 75.74 +/- 3.67 hours, respectively The mean maximum concentration of the drug in the lungs was found to be 6.2 times greater that of serum. Serum and lung tilmicosin concentrations reached peak Values 4.66 +/- 2 and 17.78 +/- 7.51 hours, respectively, after oral administration. In fowls, the apparent volume of distribution was found to be more than 1 L/kg, indicating extensive tissue distribution. The clearance Values were calculated to be 1.33 +/- 0.06 for serum and 0.11 +/- 0.004 Vh for lung.