A cohort of infants scheduled to attend the 10 month developmental assessment were studied to determine whether hearing deficits are more common in those exposed to cigarette smoke. Hearing was assessed by the standard distraction test and those with persistent abnormalities were referred to a medical audiologist. Overall 77% of infants were exposed to cigarette smoke and 40% failed the initial hearing tests. Exposure to cigarette smoke was associated with a 4.9 times increase in the prevalence of hearing deficits and 75% of the cases of hearing loss were statistically attributable to exposure to cigarette smoke. The results of this study lend further weight to the hypothesis that exposure to cigarette smoke is a cause of hearing deficits in children.