The continuum of smoking behavior among children and adolescents can be described in stages of preparation, trying, experimentation, regular smoking, and nicotine dependence or addiction. Persons who have smoked can discontinue at any stage, but quitting becomes more difficult as smokers progress through the continuum and become increasingly dependent on nicotine. Nicotine addiction is characterized by a physiologic need for nicotine, including a tolerance for nicotine, withdrawal symptoms if an attempt is made to quit, and a high probability of relapse after quitting. To determine the prevalence of selected cigarette smoking initiation and quitting behaviors among youth, CDC analyzed data from the 1997 Youth Risk Behavior Survey (YRBS). Findings indicate that among U.S. high school students in 1997, 70.2% had tried cigarette smoking. Among students who had ever tried cigarette smoking, 35.8% went on to smoke daily. Among those who had ever smoked daily, 72.9% had ever tried to quit smoking and 13.5% were former smokers.