The pharmacokinetics of tylosin were compared in cattle (Bos taurus) and buffaloes (Bubalus bubalis). Six animals received each a single dose of 10 mg/kg of tylosin tartrate by the intramuscular route. The serum concentration (Cmax) and the volume of distribution (Vd) presented significant differences between the two species. Cmax was 0.40 +/- 0.046 microg/ml for buffaloes and 0.64 +/- 0.068 microg/ml for cattle. Vd was 1.91 +/- 0.12 L/kg and 1.33 +/- 0.09 L/kg for buffaloes and cattle, respectively. However, as the present study did not show considerable differences in the pharmacokinetics of tylosin in buffaloes and cattle, similar dosage regimes of this drug can be recommended for both species.