The definition of PsA is still being refined, as is the understanding of the genetic and immunologic contributors to the pathophysiology of this disease. As knowledge of the underlying immunologic causes of PsA evolves, so too do treatment choices. Conventional therapies with broadly immunosuppressive effects have been the standard of therapy, but the clinical benefits of these agents are often unpredictable and might be limited by their side effects. Newer agents with mechanisms of action targeted toward specific components of the immune cascade are expected to provide more reliable responses with fewer efficacy-limiting side effects than the more conventional agents borrowed from the RA armamentarium. Anti-TNF medicines such as etanercept, the first agent approved specifically for treatment of PsA, are an advance in the treatment of PsA, and other biological agents are on the horizon that might continue to help define the immunopathogenesis of PsA and treat the disease effectively.