A case of herpes simplex encephalitis in a previously healthy 17-month
-old girl relapsing 1 week after completion of a 10-day acyclovir ther
apy is described. The child responded favourably to a second 10-day co
urse with acyclovir. The time of relapse and the satisfactory response
to a second course of acyclovir treatment indicate that the first cou
rse of therapy was inadequate for eradication of herpes simplex virus
infection.