Otitis media with effusion (OME) is a common condition among children and is characterized by nonpurulent fluid in the middle ear and fluctuating conductive hearing loss. Most children will spontaneously regain normal air-filled middle ears, but a certain number will have persistent problems. In our department we will treat annually about 500 children on an outpatient basis, with the insertion of ventilating tubes in the eardrum. The reason for this study was to evaluate the effect of erythromycin, instead of inserting a ventilation tube, in children with bilateral OME of longer duration than three months (double blind/placebo). The study comprises 147 children, 1–15 years of age, 83 boys and 64 girls, all with OME for more than three months. All the patients were candidates for tube insertion. In the group treated with erythromycin, 12 patients out of 69 had bilaterally air-filled middle ears after one month, as compared to 19 out of 72 in the group treated with the placebo. No difference was noted due to sex or age. The results support our indication and timing for ventilation tube insertion.