Treatment of moderate to severe Psoriasis (Pso) and Psoriasis-Arthritis (PsA) is largely confined to systemic therapy in Germany. Systemic therapy includes conventional systemic therapy (e.g. fumaric acids, methotrexate, ciclosporin A) and biological treatment (e.g. adalimumab, etanercept). While short- and middle-term efficacy of most systemic treatments has been shown in clinical studies (and is incorporated in international guidelines), knowledge about long-term outcomes, optimal treatment and effectiveness under real-world conditions is still missing. PsoBest, the German registry on the treatment of moderate to severe Pso and PsA started in 2008 and documents the long-term course of patients being administered any biologic or conventional systemic antipsoriatic drug authorized in Germany for the first time. The registry evaluates the long-term course of 3,500 patients with Pso and PsA treated with systemic antipsoriatics.