The abilities of 34 Campylobacter jejuni and 9 Campylobacter coli isolates recovered from retail meats to adhere to and invade human intestinal epithelial T84 cells were examined and compared with those of a well-characterized human clinical strain, C. jejuni 81-176, to better assess the pathogenic potential of these meat isolates. The meat isolates exhibited a wide range of adherence and invasion abilities; a few of the isolates adhered to and invaded T84 cells almost as well as did C. jejuni 81-176. There was a significant correlation between the adherence ability and the invasion ability of the Campylobacter isolates. The presence of eight putative virulence genes in these Campylobacter isolates that are potentially responsible for adherence and invasion or that encode cytolethal distending toxin was determined using PCR. All Campylobacter isolates possessed flaA, cadF, pldA, cdtA, cdtB, and cdtC, and most (91%) also contained the ciaB gene. However, the virB11 gene, carried by virulence plasmid pVir, was absent in almost all the Campylobacter isolates. Our findings indicated that C. jejuni and C. coli present in retail meat were diverse in their ability to adhere to and invade human intestinal epithelial cells and that the putative virulence genes were widespread among the Campylobacter isolates. Thus, despite of the presence of the putative virulence genes, only some but not all Campylobacter strains isolated from retail meat can effectively invade human intestinal epithelial cells in vitro.