The proportion of Escherichia coli non-susceptible to 3rd generation cephalosprins from invasive clinical samples has risen in Hungary from 5.1 per cent in 2006 to 15.5 per cent in 2011. The prevalence of ESBL-production in E. coli of animal origin remains unknown. During the first stage of a probe forty-five human and 18 animal ESBL-producing E. coli strains isolated in 2006-2007 were investigated. The human strains were representatively selected from a collection of 113 ESBL-producing isolates sent to the national reference center from local laboratories across the country. A variety of ESBLs were detected (SHV-2, -5, -12, CTX-M-32) with CTX-M-15 being the most common in human and CTX-M-1 the dominant in animal isolates. Genetic characterization revealed that thirty-six human isolates (80 per cent) belonged to either the phylogenetic group (PG) B2 or D. Conversely, 15 animal isolates (83 per cent) proved to be members of the A and B1 commensal PGs. Furthermore 46 per cent of human isolates (21/45) from 12 centres belonged to the international O25-ST131/B2 clone while nine isolates from seven centers showed the O15 serotype. Pulsed-field gel electrophoresis (PFGE) detected 22 and 11 diverse pulsotypes among 45 human and 18 animal isolates, respectively. The human and animal strains did not share any pulsotypes.