|Abstract:||Surveys of finished drinking water conducted by the U.S. EPA during 2000-2001, revealed 7 out of 16 water utilities encompassing four states, were contaminated with Aeromonas species. A Polymerase Chain reaction (PCR) based genetic characterization determined the presence of six virulence factors genes, elastase (ahyB), lipase, (pla/ lip/ lipH3/ alp-1) flagella A and B (flaA and fla B) genes, the enterotoxins, act , alt and ast genes, in these isolates. Primer sets were designed for all the target genes, except for act, which had been published previously. PCR was performed in three duplex assays using the primers to ahy B and lip, fla and alt genes, and act and ast genes together. ahyB, lip, fla alt, act, ast were present in 40 %, 86 %, 55% , 45 %, 69% and 35% of the strains, respectively. Only one isolate had all the virulence genes. More than one kind of species was isolated from some utilities. Also different combinations of virulence factors were present in different strains of the same species. However, a dominant strain having the same set of virulence factors, was usually isolated from different rounds of sampling from a single tap. These results suggest the importance of examining as many Aeromonas isolates as possible from a water sample. The results also suggest that the Aeromonas strains isolated from water utilities have the potential to be pathogenic, although, additional virulence factors, that have not yet been identified or characterized, may be needed to cause actual disease.