Abstract: Synthesis of the title compound,1-(2'-deoxy-ß-D-ribofuranosyl)-1H-imidazo[4,5-d]pyridazine- -4,7(5H,6H)-dione (1), is reported. It was synthesized in five steps, commencing with methyl 1-(ß-D-ribofuranosyl)imidazo-4,5-dicarboxylate (2). The 3',5'-hydroxyl groups of 2 was protected with a bis-silylating agent to form 3, which was then converted into the corresponding 2'-thionocarbonate derivative 5. The reduction of the latter with tri-n-butyltin hydride (to form 6), followed by silyl deprotection with tetra-n-btylammonium fluoride, afforded 7. Treatment of the latter with hydrazine hydrate yielded the target nucleoside 1.