ABSTRACT: Biologic agents are immunosuppressants that target cytokines or specific immune cell subpopulations. Many therapies interfere with the normal inflammatory cascade and with the immune system, causing an increase in the incidence of infections. In particular, treatment with tumor necrosis factor (TNF)-α antagonists in psoriasis patients is associated with an increased risk of infection caused by intracellular microorganisms. TNF-α plays an important role in host resistance against infectious and several cases of Mycobacterium tuberculosis, Listeria monocytogenes, and Pneumocystis carinii have been reported with anti-TNF-α agents. Furthermore, B and T cells are essential to the immune response; thus, their specific reduction or inhibition by targeting molecules in T-cell cutaneous lymphomas and psoriasis could increase the risk for viral, fungal, and bacterial infections. A prompt and appropriate management of infections with the emergence of biologics is essential in clinical practice.