Murine cytomegalovirus (MCMV) was found in preproductive tissues of newborn mice acutely infected with this virus. Using 3H-labeled complementary RNA (cRNA) probe made from MCMV DNA, viral genetic material clearly occupied ovarian stromal cells surrounding the follicular region but not cells of the follicle or cells in the outer tunic layers. In the testes, squamous epithelial cells external to the tunica albuginea harbored viral genetic material. The immaturity of germ line cells in testes of one-week-old mice precluded identification of these cells or examination of their involvement. The presence of viral DNA in reproductive tissue during acute infection raised the possibility that the ovary and/or testes might act as a reservoir for latent virus later in life of adult mice. Hybridization kinetics analysis of DNA isolated from ovaries and testes of 5- and 6-month-old mice latently infected with MCMV suggested that the viral genome was present in both organs.