The relationship of worksite and occupational norms about smoking to workers' attitudes toward smoking cessation was studied in a defined population. From smokers identified in a self-administered questionnaire circulated to all employees of 10 worksites in suburban Minneapolis, 447 smokers were randomly selected and interviewed. Attitudes and social norms about smoking cessation were compared by occupation and worksite using analysis of covariance, controlling for age, sex, and education. Similarly, the relationships of social norms to attitudes were examined using multiple regression analysis. Interest in quitting smoking, confidence in the ability to quit, and coworker support of prior quit attempts were equally pervasive among workers from blue collar and white collar occupations. Yet substantial differences between worksites in attitudes and norms about smoking cessation suggest the importance of the unique social milieu of individual worksites. Of particular importance is the impact of coworker discouragement of prior quit attempts, which varied across worksites and was directly related to confidence in the ability to quit and the desire to seek formal help in future quit attempts. These findings point to the relevance of intervention programs aimed at changing worksite norms about smoking and smoking cessation.