Abstract: 2'-Methylidenepyrimidine nucleoside compounds of the general formula: ##STR1## wherein R.sup.1 stands for amino or hydroxy group; R.sup.2 stands for a halogen or a lower alkyl when R.sup.1 is amino or R.sup.2 stands for an alkyl having 2 to 4 carbon atoms, an alkynyl having 2 to 4 carbon atoms or a haloalkyl when R.sup.1 is hydroxy group; and R.sup.3 stands for hydrogen or a phosphoric acid residue, or salts thereof, compositions containing one or more of these compounds and methods for production of these compounds are disclosed.Said compounds and salts thereof exhibit noticeable antitumor activities.