Spirometry is widely used to evaluate the mechanical competence of the lung-chest wall system. All normal values currently used as standards have been determined without regard to the smoking habits of the subjects (1-5). Ferris and associates (6) recently tried to establish separate criteria for spirometric performance of smokers and nonsmokers but were unable to demonstrate significant differences between the two groups. In the present study significant differences were found in the performance of several spirometric tests between cigarette smokers and nonsmokers. Evidence was also obtained to support the thesis that the impairment of ventilatory function which is associated with cigarette smoking is reversible over an extended period of time. Spirometry was performed in 410 healthy community dwelling men ranging in age from 20 to 103 years. A 13.5-liter Collins recording spirometer was used as outlined by Kory and associates (1). The subjects were divided into four groups: (1) nonsmokers, (2) current cigarette smokers, (3) former cigarette smokers, and (4) pipe and cigar smokers. The evidence that cigarette smoking impairs ventilatory function was twofold: {1) Current cigarette smokers had signifi~antly !ower vit~l capacities (VC), one second timed vital capaCIties (FEV,) and maximal voluntary ventilations than nonsmokers. {2) partial regression analyses of the data of the current cigarette smokers indicated that the greater the consumption of cigarettes the lower were the observed VC, FEVo.• and FEV, .