Documentation of psoriatic eruptions occurring with the initiation of various pharmacotherapy agents has been reported in the literature. Two such agents include lithium and beta-blocking drugs. By understanding the mechanism by which these drugs induce and exacerbate psoriasis, we may gain further understanding of the disease process of psoriasis as well as how to treat this side effect. This paper reviews the literature that has examined the mechanism by which lithium and beta-blockers may induce and exacerbate psoriasis. Mechanisms involving both immunologic and non-immunologic factors have been examined in various studies. No consensus has been reached and further investigation is needed. However, findings such as improvement with inositol supplementation in cases of lithium-induced and -exacerbated psoriasis and disparate histologic presentation of beta-blocker-induced psoriasis provide suggestions that both the origin and treatment of drug-induced psoriasis may be different than psoriasis that is unrelated to medications.