Several studies of the depth and duration of inhalation during cigarette smoking were published between the late 1970's and early 1990's. Most were brand switching studies arising from interest in compensatory smoking behaviour. These studies reported that inhalation volume remained constant when switching from higher to lower delivery cigarettes. However, these studies tended to be relatively short term and smokers' inhalation behaviour over the long-term is likely to be more significant as far as potential health consequences are concerned. Consequently, a study has been conducted with 75 established smokers of 1-17mg tar products (FTC) to establish their 'normal' inhalation behaviour while smoking. The subjects were participating in a biomarker study and stayed in a clinic for 5 days during which time they were allowed to smoke their own brand of cigarette whenever they wished. On two days (separated by at least one day) the subjects breathing pattern was measured with a Respitrace 204 respiratory inductive plethysmograph while they smoked one cigarette. This enabled the measurement of the post-puff inhalation volume, exhalation volume, inhalation time, and exhalation time for each subject after each puff on the two cigarettes. The subjects were grouped according to the FTC tar delivery of their product: 1-3mg (15 subjects); 4-6mg; 7-13mg; 14+ mg (20 subjects each). The inhalation volume for the 4-6mg group was significantly lower than both the 7-13mg and 14+ mg groups and their exhalation volume was significantly lower than the 14+ mg group (p<0.05). No other differences were found at the 95% confidence level. When tidal volume was taken into account (as an indicator of stature) there were no differences between the groups in any of the measures.