The present investigation was undertaken to improve regimens dosage of amoxycillin, chloramphenicol or trimethoprim‐sulphadiazine in Salmonella dublin infected veal calves. The pharmacokinetics of these drugs were studied after i.v., oral, and i. m. administration (bioavailability, local irritation at the injection site, volume of distribution, and elimination half life). The most important conclusion was that amoxycillin, chloramphenicol, and trimethoprim were suitable for oral administration to veal calves, although the bioavailability of chloramphenicol and trimethoprim was significantly less when concurrently administered with a milk replacer. In vitro, the antibacterial activities of these drugs were compared. Addition of trimethoprim to sulphadiazine lowered its MIC forS. dublin, but sulphadiazine reduced the killing rate compared to that of trimethoprim alone. In the efficacy studies the activities of several serum enzymes and the plasma concentrations of Fe, Zn, and Cu were measured, but it appeared, that these biochemical parameters were no better than the clinical parameters body temperature and body weight. Using optimal dosage regimens based on MIC values and blood levels, treatment with either of the three drugs was of equal efficacy.