By using antiviral chemotherapy to moderate the lethal effect of wild-type herpes simplex virus type 2 (HSV-2), a new mouse model for herpes simplex virus (HSV)-induced hydrocephalus was developed. Groups of BALB/c mice were infected either intracerebrally (i.c.) or intraperitoneally (i.p.) with a lethal dose of HSV-2. The antiviral agent 2'-fluoro-5-methylarabinosyluracil (FMAU) was administered i.p. 2 days after virus inoculation. By day 21, 80 and 71.4% of the mice infected i.c. or i.p., respectively, survived. The surviving animals were randomly subdivided into different groups and some were challenged i.c. or i.p. with a lethal or superlethal dose of homologous virus. The mice were sacrificed at 2 or 3 months after the initial virus infection. Neuropathological changes of the brains were assessed. Dilation of lateral and third ventricles was noted in the animals initially inoculated i.c., especially in all the animals inoculated i.c. and challenged i.c. with a superlethal virus inoculum, but not in those inoculated i.p. Microscopic examination of hydrocephalic brains revealed evidence of viral meningoencephalitis. Two different mechanisms of ventricular enlargement in this animal model are proposed. This model is relevant since HSV-induced cases of hydrocephalus have been reported to occur in humans and in particular neonates. Issues of virus persistence and expression, long-term evaluation for disease progression, and intervention strategies could be examined with this model.