A seriesof twenty four acyclic unsaturated 2,6-substututed purines 5a-20b were synthesized. These compounds were evaluated for cytotoxic activity against NCI-60 DTP human tumor cell line screen at 10µMconcentration. N₉-[(Z)-4'-chloro-2'-butenyl-1'-yl]-2,6-dichloropurine(5a), N₉-[4'-chloro-2'-butynyl-1'-yl]-2,6-dichloropurine(10a), N₉-[(E)-2',3'-dibromo-4'-chloro-2'-butenyl-1'-yl]-6-methoxypurine(14)and N₉-[4'-chloro-2'-butynyl-1'-yl]-6-(4-methoxyphenyl)-purine(19)exhibited highly potent cytotoxic activity with GI₅₀ values in the 1-5 µM range for most human tumor cell lines. Other compounds exhibited moderate activity.