The prevalence of atypical cytology has been determined in relation to age, smoking and asbestos exposure for male workers employed in 3 mines in the Province of Quebec. Overall participation was 71%. Out of 867 participating workers, 626 (72%) presented a deep cough specimen within normal limits, 74 (8.5%) a specimen with mild atypical metaplasia and 10 (1.2%) a specimen with moderate atypical metaplasia. Four lung carcinoma were identified. Five percent of the workers initially interviewed did not return their specimen and 12.7% had unsatisfactory test results. Proportions of cellular atypia increased with age and asbestos exposure. Using logistic regression analysis, estimated probabilities of abnormal cytology for workers aged 25 years when started mining increased with both years of asbestos exposure and exposure index measured in fibres per cubic centimeter.