Smokers are often advised to quit in a discussion of future health risks. The authors tested whether adding information about personal effects of smoking would motivate hospital outpatients to stop smoking more than advice about potential hazards would. Ninety smokers in a general screening clinic were randomized to receive education alone or education plus an additional motivational intervention that contained immediate feedback about the smoker's exhaled carbon monoxide (CO) values, spirometry results, and pulmonary symptoms. A self-report of smoking status was obtained one, four, and 12 months after the intervention. In addition, at 12 months, exhaled CO measurements were made. Smokers who received the additional motivational intervention were more than twice as likely to report quitting some time during the 12-month follow-up (40% vs. 16%, p = 0.015). At 12 months, 33% of the intervention group and 10% of the control group smokers tested had achieved CO-validated cessation (p = 0.03). Counting all patients not contacted as continuing to smoke, the percentages were 20% vs. 7% (p = 0.06). These practical feedback methods to motivate cessation deserve testing in other settings.