Objective: To estimate the relative risk for otitis media (OM) in children from environmental tobacco smoke (passive exposure), maternal smoking during pregnancy (gestational exposure), or both. Design: Analysis of data from a national cross-sectional health survey, utilizing questionnaire information and serum cotinine measurements. Participants: Children younger than 12 years (N=11728) in the Third National Health and Nutrition Examination Survey (NHANES III), conducted from 1988-1994. Main Outcome Measures: Occurrence and recurrence of ear infections. Results: The cumulative incidence of ear infections was 69%. Of all participants, 38% were exposed to passive smoke, 23% were exposed to gestational smoke, and 19% were exposed to combined passive and gestational smoke. The occurrence of any ear infection was not increased by passive smoke exposure (adjusted risk ratio [RR], 1.01; 95% confidence interval [CI], 0.95-1.06), but was slightly increased by gestational (adjusted RR, 1.08; 95% CI, 1.01-1.14) and combined (adjusted RR, 1.07; 95% CI, 1.00-1.14) smoke exposures. The risk of recurrent ear infections (≥6 lifetime episodes) was significantly increased with combined smoke exposure (adjusted RR, 1.44; 95% CI, 1.11-1.81). Other risk factors for ear infection identified in multivariable analysis were race/ethnicity, poverty-income ratio of 2.00 or more, attendance in day care, history of asthma, and presence of allergic symptoms. Conclusions: Passive smoke exposure was not associated with an increased risk of ever developing an ear infection in this study. The increased risk found with gestational and combined smoke exposures has marginal clinical significance. For recurrent ear infections, however, combined smoke exposure had a clinically and statistically significant effect.