Intake dosages of mainstream smoke components were determined in 52 smokers of low-nicotine (LN) cigarettes (42% male) and 55 smokers of medium-nicotine (MN) cigarettes (55% male) by measuring smoking profiles for each smoker using a computer-assisted pressure transducer, and then programming the profiles into a piston-driven smoking machine. No significant differences in smoking patterns were observed between smokers of LN and MN cigarettes regarding puff volume and frequency of drawing puffs, although female MN smokers had 15% less puff volume than did female LN smokers. However, for MN cigarettes, men tended to draw larger puffs than women (p<0.001) while for both cigarette types women took significantly more puffs per cigarette than did men (p<0.05). These two factors combined to cause LN smokers to draw more total smoke (puff volume x frequency) per cigarette than MN smokers, with the difference especially pronounced among women. Medium-nicotine yield smokers took in significantly more nicotine (p<0.01), CO (p<0.05), and "tar" (p<0.05) per cigarette, as well as per day (all p<0.01). MN smokers had somewhat higher dosages of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) both per cigarette (not significant, based on only 9 determinations to date) and per day (p=0.05). Urinary cotinine was significantly correlated with nicotine dose (=0.52, p<0.001). Male MN smokers had significantly more cotinine (creatinine-adjusted) in their urine than did male LN smokers (p<0.05). Pronounced sex differences were observed: female smokers of all cigarette types had significantly more cotinine in their urine than did male smokers (p<0.05), with or without adjustment for number of cigarettes smoked per day. Female smokers also had higher levels of both NNAL (p=0.06) and NNAL-glucuronide (p=0.01) than men regardless of cigarette type.