4-[1-Oxo-3-(substituted aryl)-2-propenyl]-3-phenylsydnones were condensed with hydrazine to yield fourteen 4-[5-(substituted aryl)-4,5-dihydro-1H-pyrazol-3-yl]-3-phenylsydnones. Four compounds have shown antiinflammatory activity in carrageenen-induced edema assay in rats and six compounds have shown analgesic activity in acetic-acid-induced writhing assay in mice at a dosage of 100 mg/kg po. The antiinflammatory activity of these compounds was less than the positive controls phenylbutazone and ibuprofen. However, compound 25 has shown more analgesic activity than aspirin (ED50, 28.3 vs 81.4 mg/kg respectively, po). Two compounds have shown antiarthritic activity in adjuvant-induced arthritis in rats. The ulcerogenicity of active compounds was less than phenylbutazone. © 1995 Elsevier, Paris.