Variables of smoking were measured when subjects smoked the first cigarette of the day after an eight- to 10-hour period of abstinence. The cigarettes smoked had high, medium, or low nicotine yields but the tar and carbon monoxide yields, taste, and draw characteristics remained constant. The number of puffs and interval between puffs did not differ between nicotine doses. The smokers took larger puffs, however, when smoking cigarettes delivering lower nicotine yields than their normal brands. This change in the size of puff must be attributed to the change in nicotine yield since all other characteristics of the cigarettes remained constant. Thus encouraging the smoking of low-nicotine cigarettes may increase exposure to combustion products and not appreciably decrease exposure to nicotine, since the smokers increased the size of their puffs in response to the decreased nicotine yield.