Abstract: The oligonucleotides have sufficient guanosine to form a guanosine tetrad and can be composed of at least about 40% guanosine nucleotides, the nucleotide sequence containing at least two runs of at least two guanosines. Some of the new oligonucleotides also contain phosphorothioate backbones and 3′ end modifications. Representative guanosine-rich oligonucleotides of the present invention demonstrate anti-viral activity in tissue culture against HSV-2, HIV-1, HCMV and FMLV, and show specific inhibition of bacterial RNA polymerase enzymes T7 and T3, the FMLV and HIV-1 reverse transcriptase enzyme and eukaryotic RNA polymerase.