Owing to their unique specificity, monoclonal antibodies have provided a novel approach to the treatment of human diseases. Several types of antibodies against a diverse array of pharmacological targets have been marketed and many more are currently in clinical trials. Factors related to antigen expression, target pharmacology, and antibody effector functions can contribute to the adverse event profiles observed with monoclonal antibodies. Effective translation of information gained from preclinical research and safety studies into clinical development is a crucial step for successful development of monoclonal antibodies.