In this study, new isoxazolo[4,5-d]pyridazin-4(5H)-one derivatives having an N-acylhydrazone moiety were synthesized. The compounds were tested for their COX inhibitory activities using NS-398 and indomethacine as reference compounds. Although the compounds had an inhibitory profile against both COX-1 and COX-2, most were found to be more selective against COX-2 by a small percentage of inhibition, at the concentration of 50 microM. Docking studies were done to understand the interactions of the tested compounds with the active site of COX-2. It was observed that the compounds fit into, and interacted with, the hydrophobic parts which are common in the active pocket of COX-1 and COX-2 enzymes but could not fit to the area which is specific for COX-2 enzyme.