Chronic plaque psoriasis is an immune-mediated, inflammatory skin disease with a heavy burden on quality of life of patients. The disease has a chronic relapsing course and may be life long. Comorbid disorders include psoriatic arthritis, obesity, dyslipidemia, hypertension and an increased rate of cardiovascular disease. Conventional systemic treatments include methotrexate, cyclosporine and acitretin, which are associated with end organ toxicity that precludes long term therapy. Biological drugs are designed to selectively interfere with the immune mechanisms that induce psoriasis. Efalizumab is effective for skin psoriasis but not psoriatic arthritis. Anti-TNF-alpha agents (etanercept, infliximab and adalimumab) are active on both psoriasis and psoriatic arthritis. Infliximab is the most effective and rapid agent, but its safety profile may be less favourable. Moreover, efficacy can reduce over time. Etanercept is moderately active but has a better safety profile, and can be discontinued and re-used without loss of efficacy. The long term safety of all these agents has not been established.