Seventy-eight preschool children considered to be suffering from long-standing secretory otitis media on the basis of a combination of impaired or abolished mobility of the tympanic membrane and conductive deafness, were examined consecutively. All children underwent bilateral paracentesis. Those children whose ears contained mucous secretion subsequently constituted a prospective longitudinal study group. On the same occasion as the paracentesis was performed, 24 children with bilateral or unilateral mucous secretion in their ears underwent adenoidectomy. Thirty-five non-adenoidectomized children with mucous secretion in one or both ears served as controls. Both groups were followed up for 24 months. At the end of this period they were compared with respect to the state and mobility of the eardrum, a pure tone average audiogram and middle ear impedance. No difference was detected between the two groups. It is therefore concluded that the preventive and therapeutic effects of adenoidectomy on secretory otitis media are doubtful.