We measured daily nicotine intake in 11 habitual smokers who smoked their usual brand or commercial high-yield (Federal Trade Commission [FTC] yield 1.2 mg nicotine, 16 mg tar) or low-yield (0.4 mg nicotine, 5 mg tar) cigarettes. Daily nicotine intake was measured from metabolic clearance data in conjunction with blood and urinary concentrations of nicotine during 24-hr smoking periods. On the average, subjects consumed 35 mg nicotine while smoking their usual cigarettes and 26 mg while smoking either high- or low-yield commercial cigarettes different from their usual brand. This level of nicotine consumption from low-yield cigarettes was because smokers obtained 60% more nicotine per cigarette than predicted by FTC yield and they smoked 25% more cigarettes a day. Although there was considerable variability in nicotine intake between subjects, there was a correlation within subjects between intake while smoking their usual brand and experimental cigarettes. Nicotine intake between the two commercial high- or low-yield cigarettes also correlated (r = 0.86). These findings are consistent with a minimal level of acceptable daily intake of nicotine for individuals that is related to usual intake. We suggest that our protocol provides a better quantitative estimate of the yield of different cigarette brands and potential health hazards than those currently provided by the FTC.