Previous work has shown that human yield-in-use (YIU) measurements obtained from cigarettes smoked during puff-profiling are usually greater than those obtained from cigarettes smoked outside the laboratory. The present data speak to whether these differences result from the puff-profiling hardware attached to the cigarette and/or from smoking behavior differences related to the laboratory setting. Data from two smoking behavior studies involving YIU measures demonstrate effects of both the hardware and laboratory setting.Study 1: Thirty smokers participated in two all-day sessions smoking either 14 UB (usual brand) or 14 Test cigarettes at 30 min intervals. In a given session, 5 of the 14 cigarettes were equipped for puff-profiling measurement and the other 9 cigarettes were smoked without profiling. YIU nicotine measures were significantly higher for both UB (1.92 vs. 1.68 mg/cig) and Test (1.65 vs. 1.43) cigarettes when the puff-profiling equipment was attached. Study 2: Forty-four smokers participated in three weekly sessions where they smoked three different cigarettes. On the day prior to their lab visit, they collected all butts from cigarettes smoked outside the lab (OL). In the lab, they smoked one cigarette attached to a puffprofiler probe (PP), waited 30 min, then smoked a second cigarette which was not profiled (UP). For each cigarette, YIU "tar" and nicotine followed the order: profiled > unprofiled > field. (Average YIU nicotine mg/cig.: 1.57 (PP), 1.44 (UP), 1.34 (OL); average YIU "tar" mg/ cig.: 18.0 (PP), 16.9 (UP), 13.4 (OL)). These results indicate that human yields obtained in the laboratory overestimate typical cigarette yields to the smoker and that puff profiling also leads to an additional increase in yield estimates.