Five smokers smoked a cigarette ad libitum one minute after inhaling either 0, 2, 4, 8 or 12 puffs of tobacco smoke according to a standardized smoking regimen. Heart rate and expired air carbon monoxide levels increased in a linear manner with increasing number of pretreatment puffs. Subjects took fewer puffs on, and spent less time smoking, and puffing on, the cigarette as the number of pretreatment puffs increased. The duration of individual puffs decreased with successive puffs as the cigarette was smoked, but was not affected by the puff pretreatments. Intervals between successive puffs (interpuff intervals) generally increased over the first half, and leveled off or decreased over the second half of the cigarette. Interpuff intervals occurring early in the cigarette tended to increase after the 12-puff pretreatment. The results are consistent with the suggestion that the observed increase in interpuff interval as a cigarette is smoked is the result of a satiation process.