Four clinically normal and four pneumonic Holstein Friesian calves were used to study the pharmacokinetic profile of apramycin, Apramycin concentrations in serum and urine were assayed microbiologically after intramuscular injection in normal and pneumonic calves. Following a single intravenous dose of apramycin (20 mg/kg) the blood concentration time-curve indicated a two compartment open model with an elimination half value (to B) of 2.53+0.02 hours. Following a single intramuscular dose of apramycin (20 mg/kg) the highest serum concentration occurred 2 hours post-injection with absorbtion half lives (to caß) 0.637 and 0.487 hour for normal and pneumonic calves, respectively. The elimination half lives (to B) were 2.44 hours in normal and 2.315 hours in pneumonic calves. After intra- muscular injection of apramycin at a dose of 20 mg/kg. twice aday for five consecutive days, the highest serum concentration occurred 2 hours after each dose with elimination half lives (to B) ranging from 2.24 hours to 3.18 hours in normal and from 2.31 hours to 2.78 hours in pneumonic calves. The mean systemic bioavailability was 61.98+2. 19% and the in-vitro protein biling percent of apramicin was 2.29+0.2%