ABSTRACT. Objective. To study the effectiveness of ventilation tubes on the language development in infants with persistent otitis media with effusion (OME). All existing studies addressed children 3 years of age or older. Currently, OME is detected and treated with ventilation tubes at a younger age. Because of the critical relationship between age, hearing, and language development, we conducted a study of the effects of ventilation tubes on language development in infants 1 to 2 years old with persistent OME.Design. A multicenter, randomized, controlled trial (embedded in a cohort) with 2 treatment arms: 1) treatment with ventilation tubes (VT group; n ؍ 93); or 2) with a period of watchful waiting (WW group; n ؍ 94). Hearing loss and expressive and comprehensive language were assessed every 6 months, while tympanometry and otoscopy were performed every 3 months. Other factors with potential influence on language development were also included: adenoidectomy, hospital, attending day care, sex, age at randomization, educational level of the mother, upper respiratory infections, and the native country of the parents and older siblings. The trial was designed to allow for the detection of a mean difference in language development of 3 months or more between children allocated to the VT and WW groups.Results. No relevant differences were found in expressive or comprehensive language between the 2 groups after adjustment for educational level of the mother, IQ of the child, and differences at baseline.A principal component analysis showed that in the VT group, the children with frequent complaints improved 1.6 months more in comprehensive language than those with no or some complaints. The children with favorable language stimulation, however, did not improve more than the children with less favorable stimulation. No differences were found for expressive language among the various clusters. The probability to improve >3 months in comprehensive language was .48 (95% confidence interval [CI]: .29 -.68) for children with highly educated mothers versus .09 (95% CI: .02-.30) for children whose mothers had a low educational level. In the WW group, these changes were .30 (95% CI: .14 -.53) and .14 (95% CI: .04 -.35), respectively. The probability to improve >4 months in expressive language was .52 (95% CI: .32-.71) for children with highly educated mothers versus .06 (95% CI: .01-.31) for children whose mothers had a low educational level. In the WW group these changes were .42 (95% CI: .23-.64) and .11 (95% CI: .03-.35), respectively. In addition, there were delays in expressive language in both groups compared with their age expected values.The comprehensive language of the children who were effusion-free during the follow-up (n ؍ 54) improved 1.5 months (95% CI: ؊.2-3.2) more than that of the children who had persistent effusion during the entire follow-up (n ؍ 28). No differences were found for expressive language development.Disregarding the intervention contrast, improvements in hearing seemed to be related...