Psoriasis is a chronic inflammatory skin disease of unknown etiology. In Japan, the estimated prevalence of psoriasis is 0.1–0.2% of the population; this is much lower than that in Western populations (2–3%). Most of the psoriasis that occurs in Japanese patients is psoriasis vulgaris. This is followed by psoriasis guttata, psoriasis arthropathica, psoriatic erythroderma, and generalized pustular psoriasis. Childhood psoriasis, including napkin psoriasis, is rare. Recently, the number of patients with psoriasis arthropathica has increased, rising to approximately 3–4% of Japanese psoriasis cases. The treatment options are poor in Japan, with no anthralin, tazarotene, acitretin, fumaric acid esters, or alefacept. Methotrexate is also not currently approved for the treatment of patients with psoriasis in Japan. Conventional therapies include topical agents (glucocorticoids and active vitamin D3 agents), ultraviolet (UV) radiation therapies (commonly psoralen combined with UVA, and narrowband UVB), and systemic treatments (etretinate and cyclosporine). Recently, the biological agents adalimumab, infliximab, and ustekinumab have been approved in Japan, and have been found to have remarkable clinical efficacy. Adv Psor Inflamm Skin Dis 2011;2(4):126–32.