Psoriatic arthritis (PsA) is a common unique form of inflammatory arthritis associated with psoriasis. Its exact prevalence is unknown but 5-30% of the 2-3% of subjects of the general population affected with psoriasis are developing PsA. Typically PsA presents as an oligoarticular asymmetrical arthritis with predominant distal finger joint pattern, presence of spinal involvement enthesitis and dactylitis. There is evidence that T-cells play a key role in the immunopathology of PsA as well as Psoriasis. Leflunomide, a selective pyrimidine synthesis inhibitor with the property to inhibit T-cell activation and proliferation has been shown to improve both joint and skin symptoms in patients with PsA. Significant response rates have been observed for Psoriatic Arthritis Response Criteria (PsARC), modified ACR20 and PASI 50 after 24 weeks of treatment with 20 mg/d Leflunomide orally in a randomised, placebo controlled multicenter trial (TOPAS Study). Leflunomide treatment also improved quality of life and showed a favourable safety profile. It is therefore concluded that Leflunomide offers an efficacious, well tolerated, safe, and relatively inexpensive therapeutic option for the treatment of actively inflamed joints and psoriatic skin lesions in patients with PsA.