The stimuli controlling the rate at which people smoke cigarettes have not been clearly defined. On the hypothesis that smoking is basically nicotine-seeking behavior, nicotine available to the subject was experimentally manipulated through controlling cigarette size and nicotine content. In Experiment I, subjects given their won cigarettes in whole, half, quarter, and eighth lengths, increased the number of cigarettes smoked and number of puffs to compensate for reductions in size. Satisfaction was directly related to cigarette length. In Experiment II, subjects given special cigarettes delivering 0.2 or 2.0 mg nicotine/cigarette smoked significantly more of the low than of the high nicotine cigarettes and took significantly more puffs. As in Experiment I, significantly more quarter length than full length cigarettes were smoked, but total number of puffs did not differ. These results support the hypothesis that nicotine controls smoking behavior.