We analyzed data from 1987 to 1990 National Health Interview Surveys and compared them with 1978 to 1980 National Health Interview Surveys data to determine changes in cigarette smoking prevalence by occupation. During this period, cigarette smoking prevalence declined from 31.7% to 24.2% among white-collar workers, from 43.7% to 39.2% among blue-collar workers, and from 37.2% to 34.5% among service workers. For occupational groups, the largest significant declines in smoking prevalence occurred among male sales workers (10.5 percentage points), female and male managers and administrators (9.9 and 8.7 percentage points), female professional and technical workers (8.0 percentage points), and male transportation equipment operatives (7.5 percentage points). Analyses of 1987 to 1990 detailed occupation codes revealed that roofers (57.8%) and crane and tower operators (57.6%) had the highest prevalences of cigarette smoking, whereas physicians (5.4%) and clergy (6.5%) had the lowest smoking prevalences. Since 1978 to 1980, the differences in smoking prevalence by occupation have widened, providing further evidence that smoking has moved from a relatively common behavior practiced by most segments of society to one that has become more concentrated among selected subpopulations. Health professionals need to play an important role in encouraging smoking cessation among workers and in advising management and labor about the benefits of strong work-site smoking policies.