The microbiological landscape of acute otitis media (AOM) has been relatively constant over the past half century. Because of this stability, empiric management of AOM was a common and efficient practice. Recently, there has been a proportional shift in the microbiology of AOM, bringing the choices for empiric therapy into question. Because of this shift, managed care organizations should review their formularies to ensure that they are structured to include and promote the use of appropriate antibiotics. This article explores the background and events leading up to the shift in AOM microbiology; discusses the clinical consequences and the future implications of the shift, such as increased costs associated with treatment failures, its impact on new vaccines and new-onset AOM and related disease states, such as sinusitis; and describes why these factors should be considered by managed care decision makers in their formulary deliberations.