Biomarkers of tobacco smoke exposure were measured in urine and buccal cells from 56 smokers of full-flavor low 'tar' (FFLT) cigarettes to evaluate the degree of individual variation. Biomarkers were measured while each individual smoked their usual brand of FFLT cigarette (UB) and after all smoked the same leading commercial FFLT cigarette brand (LL). Seven smokers were smoking the LL as their UB, allowing a preliminary assessment of intra-individual variability. Twenty-four hour urine collections and spot buccal mouthwash samples were taken at entry (UB samples) and after 6 weeks of smoking the leading FFLT cigarette (LL samples). Biomarkers were determined for nicotine; benzene; acrolein; 4-(N-methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK); the PAH surrogate marker pyrene; carbonyl protein adducts; and 1,3-butadiene. The results indicate substantial variability in biomarker values among smokers when smoking their UB of FFLT cigarette or when smoking the same FFLT cigarette. The within-subject variability (when smoking UB vs. LL) was smaller than between-subject variability (when smoking either the UB or LL), yet could still be substantial, even for subjects "switched" to the LL when this was also their UB. These results demonstrate the wide range of exposures to cigarette mainstream smoke components experienced when individuals smoke the same type of cigarette or even the same brand of cigarette.