Various behavioral and chemical measures were studied as potential simplified phenotyping techniques in overnight abstinent tobacco smokers. Irrespective of the machine-rated nicotine delivery (yield) of the cigarette used, there was a statistically significant correlation between the number of cigarettes consumed per day and overnight abstinence plasma cotinine concentration (r=.88) and its calculated nicotine dose per day (r=.88). Exhaled carbon monoxide (CO) levels correlated well with the number of cigarettes smoked (r=.83) and the Fagerström dependence scores (r=.85). The greater the Fagerström scores, the greater the daily cigarette consumption and plasma cotinine concentrations. After overnight abstinence, the baseline mean+/-S.D. heart rate was 62.9+/-10.0/min, the systolic blood pressure was 115.6+/-13.3 mm Hg and the diastolic blood pressure was 67.1+/-10.9 mm Hg. There were no statistically significant gender differences. Persons who were outliers on any measure are potential candidates for future genotyping studies. Preliminary guidelines of what is needed are described.