This study examined the effects of cigarette yield (Federal Trade Commission-determined deliveries of nicotine, tar and CO) on both biological exposure to smoke constituents and smoking behaviors. Smokers (N = 10) of high-yield cigarettes were switched in random order among five different commercially available cigarette brands with nicotine yields of 0.1, 0.4, 0.7, 1.1 (altered brand) and 1.0 (usual brand) mg and smoked each cigarette type for 5 days while a wide variety of assessments were performed. Steady-state cotinine and CO levels were substantially lower after 5 days of smoking ultra-low yield cigarettes (cotinine, 152 ng/ml; CO, 25 ppm) than when smoking usual-brand high-yield cigarettes (cotinine, 252 ng/ml; CO, 38 ppm). Both CO and nicotine boost (acute exposure) were related to yield. However, relative between-yield differences in all nicotine and CO exposure measures were smaller than predicted from Federal Trade Commission yield ratings. Substantial yield-related alterations were observed in smoking behavior. Subjects smoked more cigarettes and took larger and more closely spaced puffs when smoking low- as compared with high-yield cigarettes. The amount of tobacco burned per day was similar across all yield conditions. However, filter vent-blocking of ultra-low yield cigarettes did not appear to occur on a consistent basis. Subjective reports indicated poor acceptability of lower-yield cigarettes. We conclude that switching to lower-yield cigarettes brings about substantial alterations in smoking behavior which are at least partially responsible for the observed biological compensation associated with these cigarettes.