Shiga-toxin producing Escherichia coli isolated in Vietnam were examined. The 9 isolates included 5 from 400 diarrheal patients and 4 from 42 cows in 2003. No isolate carried eae gene. All human isolates except one and one of four animal isolates carried both stx1 and stx2. One of the human isolates could not be definitely identified as a Shiga-toxin producing Escherichia coli, because it showed positive for PCR using a common primer set for stx gene family and also positive for stx2d subtype, but negative for stx1, stx2 and for expression of the toxin. The serotypes of the isolates were various, but major serogroups such as O157, O26 and O111 were not found.