Psoriasis vulgaris is an inflammatory skin disease that is generally chronic and that affects between 1 % and 2 % of the population in industrialized Western countries. It is associated with a marked decline in quality of life. A wide range of treatments are currently available, although surveys conducted before the advent of biologic agents reflected a strong degree of dissatisfaction with the treatments then available. Extensive scientific evidence has been gathered on the safety of biologic agents, and this has led to a review of the role of systemic treatment in general and has allowed new therapeutic goals and strategies to be contemplated in patients with moderate-to-severe psoriasis. In this new situation, there is a need for Spanish guidelines on the treatment of moderate-to-severe psoriasis with biologic agents, drafted by consensus among specialists and ratified by the Spanish Psoriasis Group of the Spanish Academy of Dermatology and Venereology (AEDV). These guidelines should be evidence-based with regard to the pharmacologic characteristics, mechanism of action, administration route and regimen, efficacy, contraindications, adverse effects, and cost estimates of biologic agents approved for the treatment of moderate-to severe psoriasis in Spain.