Cigarette smoking remains the leading preventable cause of morbidity and premature mortality in the United States. Although the vast majority of smokers come in contact with the health care system on a regular basis, clinical smoking cessation interventions happen infrequently and in a non-systematic manner. In 1996, the Agency for Health Care Policy and Research (AHCPR) "Smoking Cessation Clinical Practice Guideline" provided detailed clinical practice recommendations based on a review of some 3,000 articles in the research literature and dozens of supporting meta-analyses. This article presents a simple four-step model for clinical smoking cessation interventions, including systematic identification of smoking status, brief cessation advice from clinicians, assessment of patient motivation, and detailed assistance for those willing to stop smoking. It also provides the empirical basis for the AHCPR Guideline recommendations.