Risk factor intervention is a useful strategy for prevention of poorly understood diseases. Fifteen studies have examined the relation of glucocorticoid and nonsteroid antiinflammatory treatments and onset or progression of Alzheimer's disease (AD). Fourteen of these studies suggest that such treatments (especially nonsteroidal agents) prevent or ameliorate symptoms of AD. Abundant circumstantial evidence implicates inflammation in the pathogenesis of AD. Inhibition of cyclooxygenases, the central action of nonsteroidal antiinflammatory drugs (but not a prominent effect of steroids), limits inflammation, but it may also alter neural metabolic pathways, resulting in cell death from excitotoxicity or oxidative stress. Randomized controlled trials are needed to determine whether steroids, nonsteroidal antiinflammatory drugs, or both can prevent or treat the symptoms of AD.