Abstract: Compounds of the class of 4-oxo-butenoic acid derivatives are disclosed along with the surprising use property of these compounds as a anti-tumor agents in humans against breast carcinoma, which include: 2-(N′-Fluoren-9-ylidene-hydrazino)-5,5-dimethyl-4-oxo-hex-2-enoic acid methyl ester (0F-06), 1-(2,4-Dimethyl-phenyl)-2,4-dihydroxy-3-(4-methyl-benzoyl)-5-oxo-2,5-dihydro-1H-pyrrole-2-carboxylic acid methyl ester (1F-07), 4-(4-Methoxy-phenyl)-2,4-dioxo-3-(phenyl-hydrazono)-butyric acid (3F-10), 4-(4-Chloro-phenyl)-2,4-dioxo-3-(phenyl-hydrazono)-butyric acid ethyl ester (3F-11), 2-Hydroxy-4-oxo-4-(2,3,5,6-tetrafluoro-4-methoxy-phenyl)-but-2-enoic acid (3F-15), and 4,4-Dihydroxy-5-(4-methyl-benzoyl)-2-phenyl-2,4-dihydro-pyrazol-3-one (3F-16) as well as some novel derivatives of these compounds claimed (see Table 2).