Two agents with remarkable inhibitory activity have been developed, namely, 5'-amino-2',5'-dideoxy-5-iodouridine (an antiviral agent) and a multisubstrate compound composed of 5'-aminoadenosine and 5'-amino thymidine connected in amide linkage by azelaic acid (an antineoplastic agent). The major thrust will be their development as potential drugs as well as elucidation of their mechanism of action. In addition the potentiation of the sensitization of neoplastic tissues and viruses to the lethal effects of radiation by some novel halogenated nucleosides will be pursued.