Some sugar modified analogs of 2'-deoxy-E-5-styryluridine triphosphates were synthesized and examined for their inhibitory effects on eukaryotic DNA polymerases and HIV-1 reverse transcriptase. Among these compounds, 3'-azido-2',3'-dideoxy-E-5-styrylUTP (6) and 2',3'-dideoxy-E-5-styrylUTP (7) showed remarkable inhibitory effects on reverse transcriptase. The mode of action and the influence of the substituent at C-5 of 2',3'-dideoxyUTP analogs will be described.