['To follow up a previous retrospective analysis in which we found the use of a pacifier to be a risk factor for recurrent acute otitis media (AOM).', 'In the present prospective study, the occurrence of AOM and the use of a pacifier were recorded in 845 children attending day care centers during a 15-month period.', 'More than three attacks of AOM occurred in 29.5% of the children younger than 2 years using pacifiers and in 20.6% of those not doing so (relative risk, 1.6; 95% confidence interval [CI], 0.6, 4.1); in children 2 to 3 years of age, the figures were 30.6% and 13.2%, respectively (relative risk, 2.9; 95% CI, 1.2, 7.3). Logistic modeling with adjustment for age and the duration of monitoring showed the occurrence of AOM to be associated with the time during which a pacifier was used. The use of a pacifier increased the annual incidence of AOM from 3.6 (95% CI, 2.5, 4.9) to 5.4 episodes (4.4, 6.6) in children younger than 2 years and from 1.9 (1.4, 2.5) to 2.7 (2.2, 3.3) in children 2 to 3 years of age. The population-attributable risk of AOM attacks due to the use of a pacifier was 176 attacks, ie, 459 to 635 attacks per year, in the youngest children and 69 attacks, ie, from 264 to 333 attacks per year, in those 2 to 3 years of age. It can be calculated that the use of a pacifier was responsible for 25% of the attacks in children younger than 3 years. Breastfeeding, parental smoking, thumb sucking, using a nursing bottle, and the social class of the family failed to show such strong associations with the occurrence of AOM.'] Does a pacifier increase the risk of recurrent acute otitis media in children in day care centers?