Certain drugs have been reported to precipitate or to exacerbate psoriasis. These cases occur mostly in patients with a history of psoriasis, although occasionally the new onset of psoriasis has followed treatment with certain drugs. The suspect drugs include lithium, beta adrenergic antagonists, antimalarials, and non-steroidal anti-inflammatory drugs (NSAID), in addition to various miscellaneous agents, including tetracycline. Evidence for these reports must be critically examined based on clinical and histological data, time course between drug intake and psoriasis exacerbation or resistance to psoriasis therapy, and response to drug rechallenge when available. The clinical context must be taken into consideration, including effects of concomitant antipsoriatic therapy, and the possible role of other triggering factors, such as infection. Controlled, prospective studies of the use of NSAID in patients with psoriasis may help to clarify their varied cutaneous effects. Further knowledge of the mechanisms involved in drug exacerbation of psoriasis may help to elucidate the etiopathogenesis of this chronic skin disorder.