The study takes up two problems: 1) Little research exists about general population interventions for smokers not ready to quit within the foreseeable future. 2) There is little evidence for smoking reduction as a behavioural goal in interventions. Interventions based on the Transtheoretical Model of Behavior Change (TTM) using computer expert-system technology yield delayed and smaller effects in smokers in the precontemplation stage of change compared to smokers in more advanced stages of change. Reducing the number of cigarettes smoked per day is currently discussed as an intermediate goal for this subgroup. Epidemiological and clinical studies revealed that smokers are able to maintain a substantial reduction. No undermining effects with respect to smoking cessation have been found. However, there are no studies that test the efficacy of behavioural interventions for smoking reduction using population based recruitment. Objectives: Testing the efficacy of TTM based interventions for general population smokers not intending to quit smoking, i.e. a smoking-reduction and a smoking-cessation tailored intervention using computerized expert-system technology.