Psoriasis is the most prevalent autoimmune disease in the U.S. * ~125 million people worldwide have psoriasis. Commonly misunderstood and interpreted as a "e;cosmetic problem, psoriasis is a complex and potentially debilitating disease; nearly 60% of people with psoriasis reported their disease to be a large problem in their everyday life. This issue of Dermatologic Clinics devoted exclusively to psoriasis is edited by two leaders of the International Psoriasis Council, Dr Alan Menter and Dr Chris Griffiths. Topics include: Genetics of psoriasis; Immunopathogenesis of psoriasis; Phenotypical expressions of psoriasis; Psoriasis as a systemic disease with multiple comorbidities; Outcomes measures in the assessment of psoriasis in clinical practice and trials; Update on topical therapies for mild to moderate psoriasis; Phototherapy and photochemotherapy (PUVA) for psoriasis; Current and future oral systemic therapies for psoriasis; Current biological therapies for psoriasis; Future biological therapies for psoriasis; Psoriatic arthritis for the dermatologist; Pharmacogenomics and the future of psoriasis therapies. This information that goes to the heart of clinical practice is equally appropriate, beyond dermatologists, for internal medicine clinicians, primary care physicians, bone & joint specialists; hematologists/oncologists, and researchers in genetic targeted therapy development.