El pdf del artículo es la versión post-print.Cyclooxygenase (COX) -1 and –2 catalyze the first step in the biosynthesis of prostanoids. COX-1 is constitutively expressed in many tissues and seems to be involved in the house keeping function of prostanoids. COX-2, the inducible isoform, accounts for the elevated production of prostaglandins in response to various inflammatory stimuli, hormones and growth factors. COX-2 expression has been also associated with cell growth regulation, tissue remodelling and carcinogenesis. More of these characteristics have been elucidate through using COX selective inhibitors. Recent advances in transgenic and gene-targeting approaches allow a sophisticated manipulation of the mouse genome by gene addition, gene deletion or gene modifications. The development of COX-2 genetically altered mice has provided models to elucidate the physiological and pathophysiological roles of this enzyme.This work was supported by grants from Instituto de Salud Carlos III (Red de Centros C03/01), Generalitat Valenciana (GRUPOS03/072), Ministerio de Educación y Ciencia (SAF2004-00957) and Comunidad de Madrid (CAM2004-GR/SAL/0388).Peer reviewed