A series of 4-(1H-indol-3-yl-methylene)-1H-pyrazol-5 (4H)-one derivatives have been synthesised. The Z structure of 4-[(1-methyl-1H-indol-3-yl) methylene]-3-phenyl-1-p-tolyl-1H- pyrazol-5-one was determined by X-ray crystallography. The antitumour activity was evaluated against five cancer cells by MTT assay.[(1H-Indol-3-yl) methylene]-1-(2, 4- dinitrophenyl)-3-methyl-1H-pyrazole-5-one and 4-{4-[(1-benzyl-1H-indol-3-yl) methylene]- ...