Of a series of 58 aliphatic nucleoside analogues, (S)-9-(2,3-dihydroxypropyl)adenine [(S)-DHPA] proved to be the most active congener, when assayed for antiviral activity in primary rabbit kidney cell cultures challenged with either vaccinia or vesicular stomatitis virus. Whereas most analogues derived from substituted purine and pyrimidine bases and bearing various hydroxy- or amino-substituted alkyl chains did not show evidence of antiviral activity at a concentration of 2 mM, (S)-DHPA inhibited both vaccinia and vesicular stomatitis virus replication at 0.05-0.1 mM. For 9-[(RS)-2,3-diazidopropyl]adenine and some di- and trihydroxybutyl analogues of DHPA, viz., 9-[(2RS,3SR)-2,3-dihydroxybutylladenine, 9-[(RS)- or 9-[(S)-3,4-dihydroxybutyl]adenine, 9-[(2S,3R)-2,3,4-trihydroxybutyl]adenine, and 3-(adenin-9-yl)-(RS)-alanine, an antiviral effect was noted at a concentration of 0.5-1 mM.