A total of 159 Escherichia coli colonies isolated from the stools of 23 healthy cats were studied for production of alpha-haemolysin (Hly), enterohaemolysin (EntHly), cytotoxic necrotizing factors (CNF1 and CNF2), verotoxins (VT) and heat-labile enterotoxin (LT). Hly+CNF1+, Hly+CNF2+, Hly+VT+ and Hly+ E. coli colonies were isolated from 12 (48%), 1 (4%), 1 (4%) and 2 (8%) respectively of the cats sampled. None of the 159 E. coli colonies produced LT or EntHly. Nine of 12 Hly+CNF1+ strains from the cats belonged to serogroup O6 and eleven to serotypes (O4:K?:H5 or H-, O6:K13:H1, O6:K53:H-, O6:K53:H1, O6:K53:H7 and O6:K14:H31) found among Hly+CNF1+ E. coli that cause urinary tract infections and sepsis in humans. Furthermore, 10 Hly+CNF1+ strains from the cats expressed the mannose-resistant haemagglutination (MRHA) type III. By contrast, the majority of nontoxigenic E. coli strains were MRHA negative and belonged to different O groups. We conclude that cats are a important reservoir of Hly+CNF1+ E. coli strains that possess similar characteristics to strains that can cause extraintestinal infections in humans and that Hly+ E. coli from cats usually do not produce shiga-like toxins with cytotoxic activity on Vero cells.