The therapeutic effectiveness of adenine arabinoside(tora-A) and its conjugate of prednisone(BR-8702-AP) was compared in Herpes simplex Virus Type 1 (HSV-1) infected BALB/C mice. The BALB/C mouse was infected with HSV-1(700 PFU/mouse) intranasally. Among mice infected intranasally with virus, a mortality rate of 100% was observed. On the oral administration of non-toxic doses of ara-A or BR-8702-AP(125 mg /kg/day) for 5 consecutive days 2 hours after virus infection, the tora-A was highly effective in reducing mortality to 0% (P<0.001) and BR-8702-AP was also effective in reducing mortality to 15% (P<0.01). In this model infection, the virus was first replicated in the lung and transmitted to the brain. Both arts-A and BR-8702-AP did not inhibit the viral replication in the lung, but they inhibited the viral transmission to the brain. However, the BR-8702-AP was less effective than the aria-A to prevent transmission of virus to brain. Therefore, the reduced mortality due to tora-A or BR-8702-AP therapy was associated with inhibition of viral transmission to brain.