Background:Disappearance of middle ear effusion is one of the most important outcomes in the treatment of acute otitis media(AOM).Aim:To evaluate the duration of effusion in AOM treated by antimicrobials and to find factors influencing it.Methods:Parents of 90 children with AOM monitored daily the disappearance of effusion with tympanometry.The children were randomly allocated to be treated with either oral amoxicillin or cefuroxime-axetil for 10 d.Daily monitoring lasted for 14 d or until the tympanogram was normal(curve A or C)in both ears.Pneumatic otoscopy was carried out every 2 wk.Results:Normal tympanograms were obtained after a median time of 7.5 d(range 1-58 d)among 75 successfully monitored patients.In two-thirds(69%)of them,effusion resolved in 14 d.The median duration of effusion did not differ significantly between the two treatment groups(8 vs 7 days,P = 0.7).The children who had unilateral AOM cured more rapidly than those with bilateral AOM(5 vs 19 d,P < 0.001).In logistic regression analysis adjusted for age,bilaterality explained treatment failure at 2 wk with an odds ratio of 28.1(95%CI 4.6-169.5,P < 0.001).Conclusion:The choice of antimicrobials did not influence the duration of middle ear effusion,which was much shorter than had been thought previously.Children with unilateral AOM were cured much more quickly than those with bilateral AOM. Background: Disappearance of middle ear effusion is one of the most important outcomes in the treatment of acute otitis media (AOM). Aim: To evaluate the duration of effusion in AOM treated by antimicrobials and to find factors influencing it. Methods: Parents of 90 children with AOM monitored daily the disappearance of effusion with tympanometry. The children were sorted allocated to be treated with either oral amoxicillin or cefuroxime-axetil for 10 d. Daily monitoring lasted for 14 days or until the tympanogram was normal (curve A or C) in both ears. Pneumatic otoscopy was carried out every 2 wk. Results: Normal tympanograms were obtained after a median time of 7.5 d (range 1-58 d) among 75 successfully monitored patients. In two-thirds (69%) of them, effusion resolved in 14 d. median length of effusion did not differ significantly between the two treatment groups (8 vs 7 days, P = 0.7). The children who had unilateral AOM cured more rapidly than those with bilateral AOM (5 vs 19 d , P <0.001) .In logis tic regression analysis adjusted for age, bilaterality explained treatment failure at 2 wk with an odds ratio of 28.1 (95% CI 4.6-169.5, P <0.001) .Conclusion: The choice of antimicrobials did not influence the duration of middle ear effusion, which was much shorter than had been thought previously. Child with unilateral AOM were cured much more than than with with bilateral AOM.