Psoriasis is a common skin disease affecting 1 - 3% of the white population. Although its physiopathogenesis still remains poorly understood, recent data suggest a key role played by memory T cells in the genesis of skin and joint lesions. Recent developments in the understanding of cellular mechanisms underlying psoriasis and in biotechnologies have given rise to a generation of biological agents that have shown clinical efficacy in treating psoriasis. These agents, including chimeric antibodies, fusion proteins and recombinant interleukins, specifically target the activated memory T cells directly involved in the development of psoriasis lesions and inhibit their action either directly or through inhibition of pro-inflammatory cytokines. Compared with conventional systemic treatments, they show a better safety profile and allow durable remissions. Some of these agents were very recently marketed for the treatment of psoriasis and hopefully others will follow. These biologicals have opened a new era for the management of this disease; they are reviewed in this article, based on data available in the literature.