Tenth grade health classes in three high schools received a special program focusing on the immediate physiological effects of cigarette smoking and the social cues influencing adoption of the smoking habit, and classes in two control schools received standard information on the long-term effects of smoking. Only subjects in the special program reported a decrease in smoking from pre to post-test; they also scored higher than controls on a knowledge test. Carbon monoxide levels were significantly lower for subjects in the special group at post-test.