Participants were aged 18�C55 years (M = 32.3, SD = 11.0) and reported smoking at least 15 cigarettes/day (M = 19.6, SD = 4.7) for at least 1 year (M = 8.0, SD = 7.1). Smoking status was confirmed with an expired-air carbon monoxide (CO) level of at least 15 ppm (M = 22.4, SD = 9.2) and an average score of 6.0 (SD = 2.0) on the Fagerstr?m further information Test for Nicotine Dependence (Heatherton, Kozlowski, Frecker, & Fagerstr?m, 1991). Participants reported smoking regular (n = 21) or light (n = 9) cigarettes (average Federal Trade Commission [FTC], 2000, method, 1.1 mg nicotine [SD = 0.3], 14.9 mg tar [SD = 3.5], and 15.0 mg CO [SD = 3.0]). Current smoking reduction, ultra-light cigarette smoking, history of chronic health or psychiatric conditions, and pregnancy or breast feeding were exclusionary criteria.

Procedures This laboratory study used a six-condition, within-subject, Latin square�Cordered design. Following verification of overnight cigarette abstinence (expired-air CO �� 10 ppm), recording of heart rate commenced. Measures of tobacco or nicotine withdrawal and CO were assessed 30 min later. Participants then smoked the first cigarette ad libitum: own brand or Merit ultra-light (Philip Morris, Richmond, VA; 0.5 mg nicotine, 5 mg tar, and 7 mg CO, FTC, 2000), covered with opaque rolling paper (Zig-Zag Orange 11/4, Louisville, KY). Cigarettes were smoked using a desktop device (two sessions), a portable device (two sessions), or no device (two sessions). All sessions were videotaped, and the proximity of the camera to the participants ensured that they were aware of the recording.

Participants had been familiarized with all measurement equipment and instructed to smoke as normal with each device at screening. After smoking, withdrawal effects and CO were assessed again. This same pattern was repeated three more times at 30-min intervals. Sessions ended with completion of an acceptability questionnaire and payment (U.S.$300 total). Outcome measures Puff topography. Puff volume, duration, number, and IPI were measured via mouthpiece-based desktop (Clinical Research Support System [CReSS]) and portable (CReSSmicro) computerized topography devices (Plowshare Technologies, Baltimore, MD. The desktop device consists of a mouthpiece connected to a metal box (21.1 �� 14.2 �� 15.2 cm) by 152.4 cm of black plastic tubing. For data collection, the metal box must be connected to a microcomputer.

The portable device is a battery-powered single unit (6.5 �� 5.5 �� 2.9 cm) that stores topography data until they are downloaded to a microcomputer. Cigarettes were placed into the devices�� mouthpiece Drug_discovery connected to a pressure transducer, and pressure changes created by an inhalation were amplified, digitized, and sampled at a rate of 1000 Hz. Software converted signals to airflow (ml/s) and integrated data over time.