Primary care physicians can play an important role in reducing tobacco smoking in the population. The general practice is a suitable setting for implementing proactive smoking interventions, because a large proportion of the population can be regularly reached in a favorable psychological state. Further, a trustful interpersonal relationship between the practitioners and their patients is supposed to increase the susceptibility to preventive measures. However, currently general practitioners are not capitalizing this advantage although evidence based treatments are available, which are effective and cost-effective. Outreach programs combining educational and practice-based measures have been found to be effective in engaging practitioners in screening and in giving advice. Computer expert-system and brief counseling interventions, which are based on the Transtheo-retical Model of behavior change (TTM), are promising approaches for the entire population of practitioners and smoking patients. For large scale implementation, data are needed about the degree of integration in every day routine clinical practice that could be achieved by implementing such interventions. Objectives: Evaluating different strategies for the implementation of proactive smoking interventions in general practices. Methods: In a randomized controlled trial, 150 randomly selected general practices of a defined German region will be included. The procedure comprises the implementation of 1) an on-site computer expert-system intervention, 2) a counseling intervention provided by the practitioner, or 3) the computer expert-system plus the counseling intervention. During an implementation phase of one month, two on site training sessions and support by phone will be provided. Routine use of the interventions will be monitored for the following 6 months. Main outcome measures are the number and rate of identified and treated smokers. A follow-up assessment will be realized 12 months after practice attendance to determine the smoking status of the treated smokers.