SummaryThe experiment was set up to make a clinical comparison in 140 pneumonic calves of two injectablc oxytetracycline formulations with different pharmacokinetic properties: Engcmycin^® 10% DD and Terramycin^® LA. The animals were examined clinically on the day of admission (day 0) and 1,2,3, 6 and 21 days thereafter. Calves were treated on day 0 with either Engemycin^® 10% DD (n=70) or Terramycin^® LA (n=70) at a dose of 20 mg/kg. If animals were not cured after one single injection, a second or even third injection was given at day 3 and day 6 respectively. No significant differences between the two treatment groups were found with regard to the number of injections needed for a complete cure, the evolution of dyspnoea, or the restoration of appetite. Thus both preparations gave comparable recovery rates. A difference between the two groups existed in the evolution of body temperature during the test period: the return to a normal body temperature occured more rapidly in the Engemycin^® 10% DD group. Regarding the tolerance aspects the degree of irritation depended in the preparation used. Calves treated with Engemycin^® 10% DD showed significantly less swelling of the injection site on day 1 then calves treated with Terramycin^® LA.