The findings in this report are subject to at least six limitations. First, the estimates understate deaths attributable to tobacco use because estimates of deaths attributable to cigar smoking, pipe smoking, and smokeless tobacco use were excluded. Although the overall prevalence rates of cigar and pipe smoking and use of smokeless tobacco have remained relatively stable, increased public health concerns about these products might warrant including estimates of deaths attributable to these tobacco products in the future. Second, RRs were based on deaths during 1982-1988 among birth cohorts who might have had different smoking histories than current or former smokers (e.g., age of initiation and duration of smoking before quitting). Third, this report used a death-certificate–based definition of COPD, including codes for bronchitis/emphysema and chronic airway obstruction (ICD-10 J44).1 Therefore, the COPD SAM estimate used for this report might differ from other estimates that use other definitions of COPD.1 Fourth, RRs were adjusted for the effects of age but not for other potential confounders. However, research suggests that education, alcohol, and other confounders had negligible additional effects on SAM estimates for lung cancer, COPD, ischemic heart disease, and cerebrovascular disease in CPS-II. Fifth, productivity losses understate the total costs of smoking because costs associated with smoking-attributable health-care expenditures, smoking-related disability, employee absenteeism, and secondhand-smoke–attributable disease morbidity and mortality were not included. Finally, the estimates do not account for the sampling variability in smoking prevalence estimates or RRs.