To compare immediate with delayed prescribing of antibiotics for acute otitis media. Open randomised controlled trial. General practices in south west England. 315 children aged between 6 months and 10 years presenting with acute otitis media. Two treatment strategies, supported by standardised advice sheets-immediate antibiotics or delayed antibiotics (antibiotic prescription to be collected at parents' discretion after 72 hours if child still not improving). Symptom resolution, absence from school or nursery, paracetamol consumption. On average, symptoms resolved after 3 days. Children prescribed antibiotics immediately had shorter illness (-1.1 days (95% confidence interval -0.54 to -1.48)), fewer nights disturbed (-0.72 (-0.30 to -1.13)), and slightly less paracetamol consumption (-0.52 spoons/day (-0.26 to -0.79)). There was no difference in school absence or pain or distress scores since benefits of antibiotics occurred mainly after the first 24 hours-when distress was less severe. Parents of 36/150 of the children given delayed prescriptions used antibiotics, and 77% were very satisfied. Fewer children in the delayed group had diarrhoea (14/150 (9%) v 25/135 (19%), chi(2)=5.2, P=0.02). Fewer parents in the delayed group believed in the effectiveness of antibiotics and in the need to see the doctor with future episodes. Immediate antibiotic prescription provided symptomatic benefit mainly after first 24 hours, when symptoms were already resolving. For children who are not very unwell systemically, a wait and see approach seems feasible and acceptable to parents and should substantially reduce the use of antibiotics for acute otitis media.