Advances in our understanding of the pathogenesis of rheumatic diseases such as rheumatoid arthritis and systemic lupus erythematosus have led to the emergence of immunoglobulin-based therapy as a major therapeutic force. Numerous monoclonal antibodies that target proinflammatory cytokines or their receptors (e.g. infliximab, adalimumab, tocilizumab, belimumab, HuMax-IL-15), and cell-surface or co-stimulatory molecules (e.g. rituximab) are either in clinical development or have been approved for clinical use. These antibodies are safe and effective in the long-term therapy of many rheumatic diseases. In addition, polyclonal immunoglobulins (intravenous immunoglobulin) obtained from pooled plasma from healthy blood donors are an effective therapeutic approach in certain rheumatic diseases. The mechanisms of action of monoclonal antibodies and intravenous immunoglobulin include cytolysis of target cells through complement or antibody-dependent cell-mediated cytotoxicity, induction of apoptosis of target cells, blockade of co-stimulatory molecules, and neutralization of pathogenic antibodies and soluble factors such as cytokines and their receptors, which ultimately lead to amelioration of the inflammatory process. The success of currently available therapeutic immunoglobulins has led to considerable interest in the identification of novel molecular therapeutic targets in rheumatic diseases.