BACKGROUND: The growing popularity of CAM among the public is coupled with an ongoing debate on its effectiveness, safety, and its implications on the reimbursement system. This issue is critically important for GPs, who have a "gatekeeping" role with respect to health care expenditure. GPs must be aware of medications' uses, limitations and possible adverse effects. Our objective was to explore GPs' knowledge of CAM and patterns of recommendation and practice, as well as the relationship between such patterns and GPs' life-styles. METHODS: A cross-sectional study was conducted in Tuscany, a region of central Italy. One hundred percent female GPs (498) and a 60% random sample of male GPs (1310) practising in the region were contacted through a self-administered postal questionnaire followed by a postal reminder and telephone interview. RESULTS: Overall response rate was 82.1%. Most respondents (58%) recommended CAM but a far smaller fraction (13%) practised it; yet 36% of CAM practitioners had no certificated training. Being female, younger age, practising in larger communities, having had some training in CAM as well as following a vegetarian or macrobiotic diet and doing physical activity were independent predictors of CAM recommendation and practice. However, 42% of GPs did not recommend CAM to patients mostly because of the insufficient evidence of its effectiveness. CONCLUSION: CAM knowledge among GPs is not as widespread as the public demand seems to require, and the scarce evidence of CAM effectiveness hinders its professional use among a considerable number of GPs. Sound research on CAM effectiveness is needed to guide physicians' behaviour, to safeguard patients' safety, and to assist policy-makers in planning regulations for CAM usage.