OBJECTIVE To explore the interaction of smoking and occupational exposure to noise as risk factors for hearing difficulty in the general population. METHODS A questionnaire was mailed to 21 201 adults of working age, selected at random from the age-sex registers of 34 British general practices, and to 993 members of the armed services, randomly selected from pay records. Questions were asked about smoking habits, years spent in a noisy occupation, difficulty in hearing conversation, and wearing of a hearing aid. Associations of hearing difficulty with smoking habit were examined by logistic regression and compared across strata of noise exposure, with adjustment for potential confounders. RESULTS Around half of the respondents had ever smoked, and half of these still smoked. Among 10 418 who provided details on hearing, 348 were classed as having moderate and 311 as having severe hearing difficulty. Risk of hearing difficulty was 3-5-fold higher in those employed for >5 years in noisy work compared with those never employed in a noisy job. Within strata of noise exposure (including those who had never worked in a noisy job), ex- and current smokers had a higher risk of hearing difficulty than lifetime non-smokers. The additional risks were small compared with those of long term noise exposure, and the combination of effects was more consistent with an additive than a multiplicative interaction. CONCLUSIONS Smoking may adversely affect hearing, and workers should be encouraged to refrain from both smoking and exposure to noise. However, the extra risk to hearing incurred by smoking in high ambient noise levels is small relative to that from the noise itself, which should be the main target for preventive measures.