Psoriatic arthritis (PsA) is now recognised as a progressively destructive inflammatory arthritis that can lead to joint deformity and functional disability. Early diagnosis and treatment with disease-modifying antirheumatic drugs (DMARDs) are necessary to control disease, particularly in patients with clinical factors and human leukocyte antigen markers predictive of progressive disease. However, there are few randomised controlled trials of the traditional DMARDs in PsA and none have demonstrated efficacy on axial manifestations or delay in radiological progression. The demonstration of raised levels of TNF-alpha in psoriatic skin and synovial tissue has provided a rationale for the application of biological agents in PsA. Furthermore, the recognition of the role of T-cell activation in both psoriasis and PsA has led to the therapeutic targeting of T lymphocytes, the results of which at this early stage are encouraging. This article reviews the studies of the most widely used traditional DMARDs in PsA followed by studies with leflunomide and the biological response modifiers, including TNF-alpha antagonists and T-cell-targeted therapies.