abs The objective of the trial was to compare the efficacy of two dry cow antibiotic products under field conditions. 43 German Holstein cows in a big farm (900 cows) with intramammary infections caused by cow- and environmental associated pathogens were allotted to two treatment groups of approximately equal number at the end of lactation. Prior tofinal milking, all quarters were double sampled for bacteriological culture and SCC analysis.Cows were dried off by abrupt cessation of milking, and dry cow therapy was administered as an intramammary infusion ofpenethamathydrojodid, benethamine-penicillin and framycetinsulfat per quarter (100 mg, 280 mg, 100 mg, Benestermycin T ^® Boehringer Ingelheim Vetmedica GmbH) or henzylpenicilline, nafcilline and dihydrostreptomycine perquarter (300,000 IU, 100 mg, 100 mg, Nafpenzal T^®, lntervet Deutsch-landGmbH) on the day of drying off. Following calving double quarter milk samples were collected between 5 to 12 DIM and againbetween 12 to 19 DIM for culture and SCC analysis. The majority of infections at dry off and new IMI was caused by coagulase-negative staphylococciand coryneforme bacteria. The cure rate was 92.3 % of quarters and the rate of new IMIwas15.5 % during the dry periodwithout significant differences between the test groups. Results of this study demonstrate that both intramammary dry-offtherapeutics are highly efficacious in curing existing infections and reducing new infections of the mammary gland during the dry period.