Abstract : Psoriasis is a multifactorial disease characterized by a cutaneous involvement possibly associated with various comorbidities. The disease associates some qualitative abnormal epidermal proliferation and immune alterations expressed by the presence of a dermal inflammatory infiltrate with neutrophil exocytosis. The hereditary aspect is well-documented and various susceptibility loci have been described on several chromosomes. The treatment relies on an eventual identifiable cause, and on the severity of the cutaneous involvement, as well as the presence of various comorbidities. The disease associates some qualitative abnormal epidermal proliferation, and an inflammatory cell infiltrate with neutrophil exocytosis. The treatment relies on a possible identifiable cause, and on the severity of the cutaneous involvement, as well as on a set of various comorbidities. Since some decades, psoriasis treatment follows a progressive step procedure. Liminar procedures rely on emollient applications. The next topical treatments concern dermocorticoids, vitamine D derivatives, calcineurin inhibitors and tars. The next step turns to photo(chemo)therapy using PUVA or UVB. In a further step, systemic treatments following oral intake include metharexate and ciclosporin. In severe cases resistant to treatments, biotherapies represent a hope for improving or even clearing the lesions. The stream of the current treatments has considerably reformed the psoriatic management over the long age.