47 cattle farms with a total of 6500 cattle in one district of Northrhine-Westfalia took part in a study on the use of antibiotic substances on a voluntary basis. The veterinary application and dispensary documents ( 13 TAHAV) as well as respecting farmers' documents (ANTHV) served as data sources. All consumption data of a one-year-period (1 September, 2006 until 31 August, 2007) were entered into a central database. The amount (free substances in kg) of substances were highest for beta-lactams (48%) followed by sulfonamides incl. trimethoprim (17%) and tetracyclines (11%). All in all about 39 kg free antibiotic substances were applied. The analysis of the treatment frequency showed similar figures: beta-lactams were used in 35% of all cattle treatments, but tetracyclines were used only in 9% of the treatments. The highest number of therapies took place against udder diseases (45% of all free substances applied, 56% of all treatment units). The therapy frequency is the average number of applied treatment units (treatment days and number of substances) per age or production group within a certain time period and population. It corresponds basically to the DDD (Defined Daily Dose) of the Netherlands as well as to the ADD (Defined Animal Daily Dose) of Denmark, although these values cannot be compared directly because of different calculation methods. Within a period of 100 days every dairy calf in the study farms achieved 0.7, every dairy cow 0.9 (including teat sealer = one day) and every fattening cattle 0.01 treatment units averagely.