The concept of rotational therapy was ﬁrst introduced by Weinstein and White (1). At that time ultraviolet B (UVB) plus tar, psoralen plus UVA (PUVA), methotrexate, and etretinate were the treatments available for severe psoriasis. Weinstein and White advocated using each form of therapy for 1-2 years and then switching to the next form. By rotating these treatments, the cumulative toxicity of each individual form of therapy could be minimized, thus reducing the carcinogenesis of PUVA, the hepatic ﬁbrosis and need for liver biopsies with methotrexate, and the musculoskeletal toxicity of retinoids. As new treatments, such as cyclosporine, were developed, they were added to the rotation, allowing further reductions in cumulative dosage over time.