Epithelial cells are targets of permissive infection by human cytomegalovirus (HCMV) in vivo during acute disease. We observed that syncytiotrophoblast (ST) cells infected with HCMV strains isolated from congenital infections induced different amount of interleukin-8 (IL-8) and immediate-early (IE) viral gene expression. This suggests that interstrain differences in HCMV-epithelial cell tropism may determine the outcome of HCMV infection. To test this hypothesis and to establish whether the permissiveness of HCMV infection in epithelial cells depends primarily on the IL-8-inducing capacity of the strain, A549 cells were infected with HCMV isolates of different origins. The data revealed that the IL- 8-inducing capacities of various HCMV isolates differed in the A549 cell cultures, and the IE gene expression and the virus production were IL-8 dose-dependent.