To study the effectiveness of adenoidectomy and tympanostomy tubes in the treatment of chronic otitis media with effusion, we randomly assigned 578 4- to 8-year-old children to receive one of the following: bilateral myringotomy and no additional treatment (group 1), tympanostomy tubes (group 2), adenoidectomy and myringotomy (group 3), or adenoidectomy and tympanostomy tubes (group 4). The 491 who accepted surgical treatment were evaluated at 6-week intervals for up to 2 years. Treatment effect was assessed by four main outcomes: time with effusion, time with hearing loss, time to first recurrence of effusion, and number of surgical re-treatments. For the groups (in order), the mean percent of time with any effusion in either ear was 49, 35, 30, 26 (p less than .0001); the mean percent of time with hearing thresholds 20 dB or greater was 19, 10, 8, and 7 (p less than .0001) in the better ear; and 38, 30, 22 and 22 in the worse ear (p less than .0001); the median number of days to first recurrence was 54, 222, 92, and 240 (p less than .0001); and the number of surgical re-treatments was 66, 36, 17, and 17 (p less than .0001). The most notable adverse sequela, purulent otorrhea, occurred in 22%, 29%, 11%, and 24% of the patients assigned to groups 1 through 4, respectively (p less than .001). In severely affected children who have chronic otitis media with effusion resistant to medical therapy, adenoidectomy is an effective treatment. Adenoidectomy plus bilateral myringotomy lowered posttreatment morbidity more than tympanostomy tubes alone and to the same degree as did adenoidectomy and tympanostomy tubes. Adenoidectomy appears to modify the underlying pathophysiology of chronic otitis media with effusion. This effect is independent of the preoperative size of the adenoid. Tympanostomy tube drainage and ventilation of the middle ear provide adequate palliation so long as the tubes remain in place and functioning. We recommend that adenoidectomy be considered in the initial surgical management of 4- to 8-year-old children with hearing loss due to chronic secretory otitis media that is refractory to medical management and, further, that the size of the adenoid not be used as a criterion for adenoidectomy. Concomitant bilateral myringotomy with suction aspiration of the middle ear contents also should be done, with or without placement of tympanostomy tubes at the discretion of the surgeon.