Smoking tobacco cigarettes results in characteristic subject-rated and physiological effects in regular tobacco smokers. Few reports have investigated potential sex differences in the physiological and subjective effects produced by tobacco smoking, though previous reports indicate that men and women differ in their tobacco smoking behavior. Sex differences in the subjective and/or physiological effects of smoking may help determine why women find quitting smoking more difficult than men and may help guide gender-specific treatment when planning smoking cessation. This laboratory study investigated sex differences in the subjective and physiological effects of cigarette smoking and smoking behavior in men (n = 38) and women (n = 30) before, during, and after they smoked two of their usual brand of cigarettes through a flowmeter-type puff topography measurement device. Results showed that the reduction in 'desire to smoke' produced by cigarette smoking was greater in women than in men, that the physiological effects of smoking were independent of smokers' sex, and that women take smaller and shorter puffs than men. These results suggest that women may be more sensitive than men to some of the subjective but not the physiological effects of smoking.