To find chemotherapeutic agents against the virus, 5-alkyluracils, 5-alkyl-isocytosines and 5-alkyl-6-methylisocytosines were synthesized. By the primary screening test on the type-1 strain of adeno virus, 5-ethyluracil, 5-butyluracil and 5-hexyl-6-methylisocytosine selected. Among the three compounds, 5-hexyl-6-methylisocytosine was effective on the type-1 strain of adeno virus for the secondary screening test, while the other two compounds did not show any effect on the virus. The all tested compounds did not show any inhibitory effect on the poliomyelitis virus and vaccinia virus.