Measurements of patterns of puffing (cigarette-holder pneumotachograph) and ventilation (plethysmography) were made in ten asymptomatic smokers during the smoking of a cigarette, on four separate occasions. There were marked individual differences and these were consistent over 3-5 weeks. In itself, the pattern of smoking could be responsible for a threefold variation in smoke intake. Puffing but not inhalation became less intense as a cigarette was smoked. It was not possible to predict indices of absorption from smoking patterns. Certain smoking patterns, e.g. small puff volume, low puff frequency, short duration of inhalation and expulsion of volume between puff and inhalation, may be less harmful than others and this may explain why some individuals remain healthy despite a lifetime of smoking.