We studied the prevalence of extended-spectrum beta-lactamase (ESBL) -producing Enterobacteriaceae in dairy calves as part of a routine health check protocol . In addition, data regarding antimicrobial use (AMU), farm hygiene, and farm management were collected in order to identify possible risks for ESBL occurrence . Ten farms participated in the study with a median of 781 milking cows (319-1701). All calves investigated were younger than two weeks with an average age of 6.8 (±3.9) days . The farms were visited and samples were collected twice at an interval of 7-11 months . Faecal samples diluted 1:10, were plated onto BrillianceTM ESBL agar in duplicates . After 24 hours at 37°C, colonies were counted and total colony forming units (cfu) /ml calculated . Bacteria species were identified biochemically . ESBL-production was phenotypically confirmed using the MICRONAUT-S β-Lactamases system . Additionally, antimicrobial susceptibility was tested using VITEK® 2 technology . Phylotyping of E. coli isolates and screening for bla genes was performed by PCR . ESBL-producing enterobacteria were detected on all farms and 96.5% of calves investigated shed ESBL-positive bacteria . Of all ESBL-producing isolates, the majority were E. coli (92.9 %), followed by Enterobacter cloacae (5.1 %) and Klebsiella pneumoniae subsp . pneumoniae (2.0 %). The majority of E. coli isolates was clearly assigned to phylogroup C (25.0 %), followed by phylogroups A (15.2 %) and E (14.1 %). CTX-M group 1 was most frequently detected (80.4 %). E. cloacae contained blaCTX-M and blaTEM or blaSHV . K. pneumoniae harboured blaSHV only . Besides resistance to penicillins and cephalosporins, the majority of isolates was also resistant to one or more antibiotic classes, with a high proportion being resistant against fluoroqinolones . 52.5% of isolates were further characterised as threefold multidrug resistant gram-negative bacteria (3MDR-GNB) according to the German Commission for Hospital Hygiene and Infection Prevention . None of the isolates were 4MDR-GNB, i.e . none revealed carbapenem-resistance . Penicillins were the most frequently administered antibiotics to calves on most farms and were the predominant substance class at herd level on all farms . Overall, the number of calves treated prior to sampling was rather low (11.7 %). Analyses of data regarding the farm management identified weaknesses in biosecurity and cleaning and disinfection . Besides beta-lactam antibiotics being the most commonly used antibiotics no other risk factors could be identified . In summary, the prevalence of ESBL-carriers in dairy calves was exceptionally high and should be motivation to develop strategies for the reduction of multidrug-resistant bacteria in farm animals.