Condensation of 1,3-diphenylpyrazole-4-carboxaldehyde (1) with some cyclic and heterocyclic active methylene derivatives afforded the condensation products 2-5. The reaction of 1 with benzoylglycine afforded the key intermediate 4-[(1,3-diphenyl-1H-pyrazol-4-yl)methylene]-2-phenyl-1,3-oxazol-5(4H)-one (6). Also, 1 reacted with malononitrile to give 7. The later reacted with 1H-indene-1,3(2H)-dione to give 9. The oxazolone 6 reacted with some aromatic and heteroaromatic amine derivatives to yield 5-[(1H-pyrazol-4-yl)methylene]-3,5-dihydro-4H-imidazol-4-one derivatives 11a,b, 12, 13 and 15. Reacting the oxazolone 6 with acetylacetone, ethyl acetoacetate, 5,5-dimethylcyclohexane-1,3-dione and 1H-indane-1,3-(2H)-dionegave the 1H-pyrazol-4-ylmethylenepyrrolidine-2,4-dione, 1H-pyrazol-4-ylmethylenepyrrol-3-one, 1H-pyrazol-4-ylmethyleneindole-3,4-dione and 1H-pyrazol-4-ylmethyleneindeno[1,2-b]pyrrole-3,4-dione derivatives 18-21 respectively. Antibacterial activity of some of the newly synthesized compounds was studded.