Definition: Acute otitis media (AOM) is defined as the presence of inflammation in the middle ear, associated with an effusion and accompanied by the rapid onset of symptoms and signs of an ear infection. This is to be differentiated from otitis media with effusion (OME), which is characterised by fluid in the middle ear, but is not associated with symptoms and signs of an acute ear infection. Persistent AOM is defined, for the purposes of this CKS topic, as occurring when people return for medical advice with the same episode of AOM, either because symptoms persist after initial management or because symptoms are worsening. Recurrent AOM is generally defined as three or more well-documented and separate AOM episodes in the preceding 6 months, or four or more episodes in the preceding 12 months with at least one episode in the past 6 months.