The past several decades have seen the advent and rapidly expanding use of biological agents in the treatment of chronic disease states. As increasingly large pools of patients have been enrolled in treatment protocols using these agents, physicians have become acquainted with both desired and adverse events associated with their use. Dermatologists frequently encounter patients affected by cutaneous drug reactions associated with the use of biological agents, thereby becoming familiar with the full range of side effects reported in the literature. This review discusses these adverse cutaneous effects, their underlying mechanisms, and efforts to predict and minimize their occurrence.