Most former cigarette smokers in the United States have stopped without formal assistance. However, a large proportion of smokers desire and seek help other than by attending formal programs. It is important to recognize what factors are likely to influence the effectiveness of smoking cessation attempts among these persons. The authors report results of a prospective cohort study of 1,552 smokers who called a stop smoking hotline to request self-help smoking cessation information. The participants were classified into three groups based on reports at the 6-month followup: 242 quitters, 497 recidivists, and 813 nonquitters. Baseline and followup data were used to evaluate three comparisons: quitters versus nonquitters, quitters versus recidivists, and recidivists versus nonquitters. Nonquitters appear to be less motivated and more doubtful of their abilities to quit successfully compared with the other two groups. Quitters appear to live in a supportive environment for smoking cessation. Heavier smokers are more hesitant to try to quit, but once they make an attempt they are as likely to succeed as lighter smokers, when other factors are kept constant. Efforts to promote environments supportive of smoking cessation are likely to result in a larger number of successful quitters. Similarly, efforts to strengthen motivation and belief in personal ability to quit are likely to encourage more nonquitters to attempt to stop smoking. Finally, it appears that some smokers need a previous quit attempt before they are able to maintain cessation successfully.