This study examined the effects of work-site health promotion on employee absenteeism. Thirty-two work sites were randomized to programs for weight control and smoking cessation or to no treatment for 2 years. The prevalence of self-reported absences from work was assessed at baseline and follow-up. Results using work site as the unit of analysis showed a net reduction in the percent of workers reporting a sick day in the last month in treatment versus control work sites of 3.7% (P = .04) and 3.4% (P = .06) in cross-sectional and cohort analysis, respectively. Further analyses found that the rate of participation in smoking (P = .09) but not weight programs (P = .72) was positively associated with change in sick day prevalence and that this effect was strongest in baseline smokers (P = .002). It is concluded that work-site smoking cessation programs may yield important short-term economic benefits by reducing employee absenteeism.