Here we characterize cHV68 infection of endothelial cells. To date, in vitro infection of most cells with cHV68 supports significant viral replication and results in complete cell lysis (data not shown, van Dyk). We have infected both primary endothelial cells and endothelial cell lines and demonstrated that they produce comparable amounts of virus as fibroblasts. However, whereas fibroblasts were mostly lysed by 36-48 hours post-infection, a significant percentage of infected endothelial cells remained intact. Analysis of endothelial cell lines revealed that these intact cells 1) were actively infected and undergoing the lytic transcriptional program, 2) continued to proliferate for a prolonged time after infection, 3) were altered in morphology and cell-surface protein expression, compared to uninfected endothelial cells, and 4) continued to release infectious virions as far as 30 days postinfection. In the absence of the cHV68 viral cyclin, endothelial cell viability was significantly decreased after infection, indicating that an active viral process was responsible for promoting the outcome of infection in endothelial cells. Of major significance, we also provided evidence of endothelial cell infection in primary cells and in vivo in immune-deficient mice. These data demonstrated that endothelial cells supported persistent, productive gammaherpesvirus infection, an outcome not previously reported for cHV68 or other gammaherpesviruses. Together, these data indicated the potential of the endothelial cell as a critical cell type in cHV68 pathogenesis, and open a new avenue of research into herpesvirus manipulation of endothelial cell biology.