Objectives. This study examined the prevalence of occasional smoking in a population of working adults, compared the characteristics of occasional and daily smokers, and prospectively examined the long-term smoking patterns of occasional smokers. Methods. At 32 Minnesota work sites, 5681 randomly selected workers were surveyed at baseline; 5248 of these were surveyed again 2 years later. A cross-sectional sample of 5817 workers was also surveyed at follow-up. Results. Occasional smokers constituted 18.3% of all smokers in the baseline sample and 21.5% of all smokers in the cross-sectional sample surveyed 2 years later. Baseline occasional smokers were significantly more likely than daily smokers to have quit at follow-up. Job monotony or repetitiveness was related to an increase to daily smoking at follow-up among baseline occasional smokers, and a change to a more restrictive workplace smoking policy was associated with quitting. Conclusions. The results confirm that a substantial proportion of smokers are low-rate users and suggest that the proportion may be rising. Further research on this group is warranted.