The present invention provides antineoplastic .alpha.-methylene-.gamma.-butyrolactones represented by the general formula \x9bI! wherein R.sub.1 is a phenyl group optionally substituted with one or two groups selected from the group consisting of halide, (C.sub.1 -C.sub.4)alkyl, (C.sub.1 -C.sub.4)alkoxy, phenyl, nitro and amino;.sub.2 R represents hydrogen, halide, (C.sub.1 -C.sub.4)alkyl or benzyl; X represents N; or wherein R.sub.1 is a phenyl group optionally substituted with one or two groups selected from the group consisting of halide, (C.sub.1 -C.sub.4)alkyl, (C.sub.1 -C.sub.4) alkoxy, nitro and amino; R.sub.2 represents Cl, F, or benzyl; X represents CH. These .alpha.-methylene-.gamma.-butyrolactones may be administered with an inert diluent or with a pharmaceutically acceptable carrier in controlling the growth of a neoplasm in a patient afflicted with a neoplasm disease. ##STR1##