Epidemiological studies indicate that anti-inflammatory drugs, especially the non-steroidal anti-inflammatory drugs (NSAIDs), decrease the risk of developing Alzheimer's disease (AD). Their beneficial effects may be due to interference in the chronic inflammatory reaction, that takes place in AD. The best-characterized action of NSAIDs is the inhibition of cyclooxygenase (COX). There is special interest for anti-inflammatory treatment of AD using selective COX-2 inhibitors. These inhibitors reduce the inflammatory reaction but lack the side effects observed with non-selective NSAIDs. So far, clinical trials designed to inhibit inflammation or COX-2 activity have failed in the treatment of AD patients. Several lines of evidence can explain the failures of the anti-inflammatory and anti-COX-2 trials on AD patients. In this review we will focus on the role, expression and regulation of COX-1 and COX-2 in AD brain. Understanding the role of COX in AD pathogenesis could contribute to the development of an anti-inflammatory therapy for the treatment or prevention of AD.