SummaryComparative studies on some selected pharmacokinetic parameters of rolitetracycline (effective antimicrobial activity levels) in sheep, pigs, rabbits, chickens and pigeons were carried out after intravenous administration of the drug at a dose of 5 mg/kg. The results revealed that a two‐compartment open model was usually optimal. Interspecies differences in the rate (α) and the volume of distribution (Vda), the area under the serum concentration time curve (AUC) and the total body clearance (ClB) were small. The values of the elimination half‐life (t 1/2β) found in sheep, pigs, rabbits, chickens and pigeons were 1.51, 3.06, 2.18, 4.33 and 2.51 h respectively. These results and data in mice, rabbits and man taken from literature were analysed to determine any correlation to body mass (W). The log of the elimination half‐life values (log t 1/2β) of rolitetetracycline revealed a significant correlation with log values of (W) between animal species. This relationship was described by the equation t 1/2β= 1.27. W0.29(r = 0.93, P<0.01, n = 5) for mammal species and t 1/2β= 1.81. W0.24(r = 0.78, P<0.05, n = 7) for mammal and bi