The biologic treatment infliximab and etanercept have recently been introduced for treatment of PsA and psoriasis, and current data indicate a higher efficacy than with previously available therapies. No clinical trials on adalimumab in PsA are yet published (2005), but preliminary data are encouraging. The improved treatment options have increased the need for sensitive methods for diagnosis, monitoring and prognostication of PsA, so that the efficient therapies can be initiated at the optimal time point and monitored optimally. Ultrasonography (US) and magnetic resonance imaging (MRI) and a number of biomarkers are promising, but not yet sufficiently studied, methods for this.