The present study was carried out to determine the clinical course of acute otitis media (AOM) in children and to analyze the risk factors that lead to persistent effusion. One hundred and twenty children aged 9 months to 10 years diagnosed as having AOM were included in this study. Sixty-two children (52%) recovered from AOM without middle ear effusions within a month. In 26 cases (22%), middle ear effusions resolved after 1 to 3 months, while 32 children (26%) had persistent effusions for more than 3 months after the onset of acute inflammation. Statistical analysis between the group showing quick recovery and that with persistent effusion was carried out in relation to various clinical factors at the onset. The significant risk factors were: younger age, bilateral AOM, presence of otorrhea, tympanogram type B or C2 on an AOM ear. Moreover, the most significant prognostic factor was a tympanogram type B or C2 on an opposite ear at the acute onset. On the other hand, factors such as sex, fever, history of otitis media, season at onset or complications did not correlate with the duration of persistent effusion. From these results we conclude that careful examination should be performed not only on the ear with AOM but also on the opposite ear in order to predict the course of otitis media.