Objective: Smokers who are not ready to quit are a very difficult group to treat. Physicians, nurses, and nurse practitioners are in a unique position to encourage patients to quit smoking. However, the best approach to do so is not clear., Methods: A two-group randomized controlled trial with 218 pack-a-day precontemplative and contemplative smokers recruited from the community. The laboratory-based study was designed to simulate outpatient visits to general practitioners. Participants were randomized to a 15-min intervention to compare the effectiveness of brief motivational or prescriptive counseling by a health professional. Thirteen outcome variables included intentions to quit and verbal reports at 1 and 6 months with biological verification. A composite outcome measure was constructed to provide greater power to detect study differences., Results: Approximately 33% of the sample reported at least one 24-h quit period during the 6 months they were followed after the trial. Results suggest that while neither treatment was superior, there were subgroup differences. Participants in the motivational condition were also more likely to respond to follow-up calls., Conclusions and Practice Implications: Motivational interviewing and prescriptive advice were equally effective for precontemplative and contemplative smokers. Practitioners should use the method that appeals to them., (Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.)