Abstract: Effects of CC and ACV on latent HSV in trigeminal ganglia were studied by reactivated HSV-1 model in vitro. Both CC (10 μg/ml) and ACV (2.5 μg/ml) were shown to significantly inhibit the reactivation of the latent HSV in infected ganglia. The effect of CC 25 μg/ml was as strong as that of ACV 10 μg/ml, but the effect of CC did not last as long as that of ACV after removal of the drugs. The latent state of HSV in vitro was dependent upon the continuous presence of either drug. Even though either drug was discontinuously administered, the latent HSV was not eliminated completely from the trigeminal ganglia. Its titers, however, were significantly reduced. The combination of CC and ACV showed a synergistic effect on preventing the reactivation of the latent HSV in vitro.