A descriptive retrospective analysis of 811 antibiograms in dogs and cats was carried out in order to get a better insight into the prevalence of antimicrobial resistance against 'critically important antimicrobials with highest priority for human medicine' in dogs and cats. A veterinary diagnostic laboratory performed antimicrobial susceptibility testing on 811 Escherichia coli isolates obtained from veterinary clinical samples from dogs and cats in Flanders, Belgium. These isolates were mainly from fecal ( 62.5%) or urogenital (30.5%) origin. A disk diffusion method with breakpoints provided by the supplier of the antibiotic disks was used for antimicrobial susceptibility testing. The results indicated that 9.5% of the Escherichia coli isolates were resistant against or intermediate susceptible to marbo-floxacine, 16.7% to enrofloxacine and 15.7% to cefovecin. The unexpected difference in resistance between marbofloxacine and enrofloxacin may be, at least partially, explained by the different clinical breakpoints used to interpret the results of sensitivity tests for dog and cat isolates in both agents. The observed resistance in this study might be related to the regular use of fluoroquinolones and third generation cephalosporins. Therefore, the use of 'critically important antimicrobials with highest priority for human medicine' remains an important issue in small animal veterinary medicine