The development programmes of different TNF-blocking agents in psoriatic arthritis (PsA) not only provided substantial evidence for the therapeutic benefits of the specific treatment options, but also enabled new insights into the differential treatment effects on distinct disease manifestations. For the first time, specific robust evidence for distinctive effects on different manifestations of PsA, as a distinct entity separate from rheumatoid arthritis (RA), has been generated in a standardized way. The clearest evidence was shown for an effect on peripheral arthritis (polyarticular) with ACR20 response rates from 45 up to 58% (vs. 9-24% for placebo), and an inhibition of radiographic progression demonstrated for the first time for a treatment principle in PsA. However, as PsA does not remain confined to the peripheral joints, it was necessary to address diverse patterns of PsA-subtypes in the outcome measurements of the anti-TNF trials. Accordingly, the results of the clinical studies on anti-TNF treatment also have demonstrated efficacy on enthesitis, dactylitis and skin psoriasis, either in sub analysis of results from phase III RCTs, or in additional prospective studies.