The cyclooxygenase (COX) isozymes are membrane-bound enzymes in the endoplasmic reticulum that catalyze two sequential reactions, cyclooxygenation and peroxidation, in the biotransformation of arachidonic acid to prostaglandin H2 (PGH2), which in turn mediates the typical inflammation symptoms. From the isozymes of the COX family, COX-1 is expressed in many tissues, and the PGs produced by it are essential for functions such as protection of the gastric mucosa, regulation of renal blood flow, and platelet aggregation. On the other hand, COX-2 is absent in most normal tissues, but its expression is induced by various stimuli that increase PG production in inflamed and neoplastic tissues. The therapeutic anti-inflammatory effects of nonsteroidal anti-inflammatory drugs (NSAIDs) are due to inhibition of the COX-2 enzyme, while most of the undesired effects stem from inhibiting COX-1. Furthermore, COX2 has been considered a possible target for preventing and treating solid tumors. Thus, selective inhibitors of COX-2 are highly desirable.