Invasive pneumococcal disease (IPD) refers to pneumonia, meningitis, bacteremia, and infections of other normally sterile sites with Streptococcus pneumoniae. Among infectious diseases, IPD is a leading cause of morbidity and mortality in children and adults. The incidence, severity, and mortality of IPD vary widely depending on several factors, some host-related, and others organism-related. After vaccine introduction, rates of IPD because of vaccine serotypes have dramatically decreased among children in the vaccine target and among nonvaccine children and adults. However, rates of IPD because of new emerging nonvaccine serotypes have increased. Continuous monitoring and surveillance studies focused on the clinical and molecular epidemiology of IPD will be required to understand the impact of the new vaccines and any possible modifications in the pattern of disease presentation. Copyright © 2012 by Lippincott Williams & Wilkins.