This study evaluated the impact of a year-long incentives-based worksite smoking-cessation program. Nineteen moderate-sized worksites, employing a total of approximately 1100 smokers, were randomized to Incentive or No Incentive conditions. All identified smokers in the worksite were considered as subjects, whether or not they participated in the intervention. Analyses were conducted at both the worksite and individual level, and using both self-reported and biochemically validated cessation as endpoints. The incentive program did not significantly improve cessation rates at either the 1-year or 2-year follow-up assessments. We conclude that more broadly focused interventions that also address worksite smoking policies, skills training, and cessation resources, or programs that target additional risk factors are needed to substantially enhance quit rates.