The relationships between tobacco smoking and both alcohol and drug consumption were investigated in 2 431 healthy individuals aged 18-29 y. We used a questionnaire to evaluate smoking habits and alcohol and drug intake, and these parameters (i.e., cotinine-to-creatinine concentration ratio, amphetamines, cannabinoids, opiates, and cocaine) were quantified via urine analyses. Urinary cotinine concentration was significantly higher in current smokers (mean +/- standard deviation: 717 +/- 61 ng/mg creatinine, n = 881) than in non- or exsmokers (32 +/- 16 ng/mg creatinine, n = 1550). Information gleaned from the questionnaires revealed that there was a greater proportion of current smokers among consumers of alcohol than among nonconsumers. Significantly (p < .001) more current smokers than non- or exsmokers self-reported that they consumed sedatives, stimulants, or illegal drugs. Urinary cotinine concentrations were highest in consumers of alcohol and in self-reported consumers of sedatives (p < .0001), stimulants (p = .01), and illegal drugs (p < .0001). We found higher urinary cotinine concentrations in subjects who had positive urinary amphetamines, cannabinoids, or opiates. Even though the prevalence of alcohol and drug consumption remained low in the population we studied, such behaviors were clearly related to tobacco smoking.