The World Health Organization lists antimicrobial substances which are essential for the treatment of specific infections in humans as "highest priority critically important antimicrobials" (HPCIAs): macrolides, fluoroquinolones, 3rd and 4th generation cephalosporins as well as glycopeptid antibacterials. The use of these substances in livestock husbandry should be restricted in order to minimise the risk of antimicrobial resistance. To date, there is little knowledge about the amounts of HPCIAs used in animal husbandry and the different animal species and diagnoses these antimicrobials are prescribed for. In a retrospective study, drug application data recorded from 2008 until 2011 from 75 conventional pig farms were evaluated. Data were assessed directly by the farmer at farm-level. The annual antimicrobial consumption was expressed in "weight of active substance(s) in [mg]" and "number of Daily Doses". Results were referred to the animal biomass, evaluated per pig age class (piglets, weaners, fattening pigs < 60 kg biomass; fattening pigs > 60 kg biomass, sows, boars) and broken down to some variables such as the substance class and the therapy indication. The focus was especially laid on the HPCIAs. The total usage of the HPCIAs in the study population was on average 3.0 mg/ kg/year; 1.1 UDD(kg)/kg/year; 0.2 ADD(kg)/kg/year and 0.6 PrDD(kg)/kg/year. This represents about 9%, 22%, 12% and 22% of total antimicrobial consumption, respectively, depending on the unit of measurement. Fattening farms showed the highest consumption of the named substances. The main part of the HPCIAs (nADD(kg)/year) was applied to weaners, piglets and fattening pigs < 60 kg. They played an important role in the therapies of piglets (approximately 40% of the total antimicrobial consumption in piglets). Macrolides played the major role within the HPCIAs and were mainly used for digestive tract diseases. A not negligible portion of macrolides was prescribed for metaphylactic and prophylactic measures.