Occupational and sex differences in the prevalence of smoking, smoking cessation, and attempts to quit smoking were studied cross-sectionally among employees of ten work sites (N = 3035). Comparisons by sex, occupation, and work site, controlling for age, were made using analysis of covariance. For both sexes, smoking prevalence was highest among blue collar workers and lowest among professionals. Successful cessation was most prevalent among professionals. At all occupational levels, smoking prevalence was higher in women than men. Although men were more likely to be exsmokers, no significant sex differences were found in the rate of recent cessation. Also, significant differences between worksites were found in the prevalences of smoking and overall cessation and in quit rates in the last two years. The high prevalence of smoking and the low interest in quitting among blue collar respondents indicate an important target for future work site interventions.