To date there is ample evidence suggesting a crucial role for respiratory viruses in the pathogenesis of AOM. Respiratory viral infection appears to initiate the cascade of events that finally leads to development of AOM (Fig. 1). The pathogenesis of AOM is complicated, involving a network of factors, some probably not yet identified, which affect each other in a time-dependent manner. Increased knowledge of the detailed mechanisms of viral infection, the host inflammatory response during URI and the interaction between viruses and bacteria could lead to major advances in the prevention of AOM.