Smoking and tobacco addiction are serious public health problems worldwide. New research reveals that addiction to tobacco can begin very early, with very low levels of smoking. Family physicians are in a unique position to prevent smoking initiation by youths and to diagnose and treat tobacco addiction in young smokers. In this paper we discuss the factors that prompt youths to try smoking, how quickly addiction to tobacco begins after the onset of smoking, how a family physician can determine whether a young patient is addicted, and what the physician can do to prevent adolescent patients from beginning to smoke or to assist them to quit if they already smoke.