Bacteriological examination of fecal samples from diarrheic dogs invariably results in the isolation ofEscherichia coli. The association of the presence of this bacterium with enteric disease in dogs is not clear. In thisstudy, the association between the presence of E. coli virulence genes and diarrhea in dogs was confirmed. For thispurpose, E. coli isolates recovered from the feces of 34 healthy dogs and 25 dogs with diarrhea aged 7.5 months to10 years, were tested for the presence of 17 virulence genes. Virulence genes were not detected in 15 of the 25 and15 of the 34 isolates from dogs with or without diarrhea, respectively. In the other isolates, the presence of genesencoding the toxins cytotoxic necrotising factor (CNF) 1, CNF2, verotoxin (VT) 1 and VT2 and/or the adhesinsintimine, F5 fimbriae and F41 fimbriae was demonstrated. There was, however, no significant difference in theprevalence of virulence genes between E. coli isolates from the diarrheic and non-diarrheic adult dogs examined.Because diagnostic markers in the E. coli isolates are absent, the examination of canine feces on the presence ofthis bacterium is of little diagnostic value.