A series of 1-acetyl/propyl-3-aryl-5-(5-chloro-3-methyl-1-phenyl-1H- pyrazol-4-yl)-2-pyrazolines were synthesized in one step by condensing suitably substituted propenones, hydrazine and acetic/propionic acid. The newly synthesized pyrazolines were characterized by analytical and spectral data. The new compounds were screened for analgesic and anti-inflammatory activity and most of them showed good activity comparable with that of standard drugs Pentazocin and Diclofinac sodium respectively. © 2010 Elsevier Masson SAS. All rights reserved.