alkali metal or alkaline earth metal salt of 2 u2032 3 u2032 dideoxy 2 u2032 3 u2032 didehydroinosine which comprises crystallizing the alkali metal or alkaline earth metal salt of 2 u2032 3 u2032 dideoxy 2 u2032 3 u2032 didehydroinosine from a solution of alkali metal or alkaline earth metal salt of 2 u2032 3 u2032 dideoxy 2 u2032 3 u2032 didehydroinosine in a solvent selected from alcoholic solvents such as methanol ethanol isopropyl alcohol tert butyl alcohol and n butyl alcohol water ethyl acetate acetonitrile and a mixture thereof a preferable solvent is selected from the group consisting of methanol ethanol water and a mixture thereof a preferable alkali metal ion is na or k and a more preferable alkali metal ion is na a preferable alkaline earth metal ion is mg 2 preferably the invention particularly relates to a novel crystalline 2 u2032 3 u2032 dideoxy 2 u2032 3 u2032 didehydroinosine sodium salt of the formula iia crystalline 2 u2032 3 u2032 dideoxy 2 u2032 3 u2032 didehydroinosine sodium salt is characterized by an x ray powder diffraction spectrum having peaks expressed as 2 u03b8 at about 15 6 17 3 18 0 21 5 23 4 24 7 27 2.