The study elucidated the pharmacokinetics of streptomycin in healthy lactating she-buffaloes after a single intramuscular (IM) injection (10 mg/kg). The drug attained its peak concentrations of 24.39 +/- 2.67, 0.45 +/- 0.05 and 5.06 +/- 0.18 micrograms/ml at 1, 4 and 1 hour in plasma, milk and uterine fluid respectively. Calculations based on the assumption of a 2-compartment model gave a plasma t1/2 (beta) of 4.01 +/- 0.44 h and an apparent volume of distribution [Vd(area)] of 0.47 +/- 0.06 1/kg. The drug was detectable in the plasma, milk and uterine fluid for 30, 8 and 12 hours, respectively. A therapeutic concentration of the drug was maintained for 6 to 7 hours in the plasma and for around 1 hour only in the uterine fluid. However, a therapeutic level could not be achieved in milk at any time. The results suggest that the drug can be used clinically by the IM route against streptomycin susceptible systemic infections but not those in the uterus and mammary gland.