Abstract: A series of 9-(N⁴-substituted acetaldehvde thiosemicarbazone)adenines weresynthesized and evaluated for antiherpes virus activity.Compounds 4a～1 were prepared bycondensation of 9-(acetaldehyde)adenine(6)and the corresponding N⁴-substituted thiosemicarbazides(10).The antiviral effects of all compounds 4a～1 were tested in vitro in primary rabbit kidney cellcultures infected with herpes simplex virus type 1(HSV-1)and varicella-herpes zoster virus(VZV),and in primary human embryo cell cultures infected with herpes simplex virus type 2 (HSV-2).Theresults showed that the minimum inhibitory concentrations(MIC)of 4e and 4f for HSV-1 and VZVwere 20,40,20 and 20 μg·ml^-1,respectively,and other compounds were 200μg·ml^-1.For HSV-2,the MIC of all tested compounds were 300 μg·ml^-1.We also evaluated the antiherpetic effect of 4e(and 4f)by combination with acyclovir(ACV)in the ratio of 1:1 in vitro.The MIC of the combinedcompounds were 2 μg·ml^-1 for 4e and 6μg·ml^-1 for 4f,while their minimum cytotoxicities(MCC)in the cell were markedly reduced compared with the individual compounds.