The management of inflammatory arthritis has been revolutionized by the use of biologic therapy. However, an important safety issue has been identified with regard to the risk of serious and opportunistic infections with biologic therapy. This review aims to summarize the most recent data available in the field. The risk of infection in inflammatory arthritis is partly determined by the nature of the underlying disease, comorbidities and other immunosuppressive treatments, in particular glucocorticoids. Data are conflicting with regard to the absolute risk of infection with biologic agents, as a result of differing study methodologies, classification of outcomes and patient populations. There appear to be some differences in risk of infection between biologic agents, which relate to their varying modes of action. Long-term observational data about the risk of infection and biologic therapy continue to emerge, although there are inherent limitations with this type of data. The process of determining the risk of infection for an individual patient should incorporate a range of factors, which may contribute to the infection risk.