Population surveys have observed decreases in cigarette use over time among smokers. These decreases have probably been influenced by tobacco control measures implemented over the past several decades, but few data exist on whether smokers have also reduced their nicotine intake. The authors examined data from two cross-sectional National Health and Nutrition Examination Surveys (NHANES), conducted in 1988-1994 and 1999-2002. Laboratory, examination, and interview data from current smokers not reporting nicotine intake from other sources were examined. From NHANES III (1988-1994) to NHANES 1999-2002, the average number of cigarettes smoked per day (CPD) fell by nearly 15% (three cigarettes), while the mean serum cotinine level fell by 13% (30 ng/ml). Finer breakdowns of CPD data in each time period suggested that most of the change occurred in the lower (<10 CPD) and higher (>or=20 CPD) smoking categories. These data suggest that CPD may represent a proxy for exposure to nicotine and perhaps other tobacco smoke constituents on the population level, since the decline in serum cotinine levels observed among smokers closely paralleled the decline in self-reported CPD between 1988-1994 and 1999-2002. In addition, these data are inconsistent with the hypothesis that the remaining population of smokers is becoming more dependent on nicotine over time.