Cytomegalovirus (CMV) is a widespread virus, characterized by the establishment of lifelong latency. In healthy individuals the infection is typically asymptomatic, however, in immunocompromised persons and in congenitally infected children CMV infection can lead to a life-threatening condition. Congenital CMV infection is the most common intrauterine infection that can affect brain development and cause permanent neurological disabilities. So far, it was clear that CMV can infect most brain cell types in vitro to a certain level, but whether this is also true in vivo and whether the infection is productive remains unknown. Thus, the main objective of this thesis was to determine whether CMV infects astrocytes in vivo and whether astrocytes support successful viral replication, using a mouse model of congenital infection. In this research we have used wild-type mice and mouse cytomegalovirus (MCMV), but also a conditional Cre/loxP reporter system, consisting of recombinant MCMV-flox virus and transgenic mouse strain in which Cre recombinase is active only in astrocytes. After MCMV infection of newborn mice and organ harvesting at certain time points, analysis of astrocyte infection was performed using immunohistochemical staining, as well as determination of brain virus titers by plaque assay. The results obtained from this study confirmed that MCMV successfully infects astrocytes in vivo, moreover, at the peak of infection in the brain, a third of the infected cells were astrocytes. In addition, it has been shown that astrocytes support productive CMV infection in vivo and that they contribute to virus spread throughout the brain. These findings contribute to a better understanding of the neuropathogenesis of congenital CMV infection and are raising new questions about the impact of infection on astrocyte function and the role of other brain cell types during infection.