A telephone questionnaire on primary prevention and cancer screening practices of general practitioners in the Rhône was administered to a sample of 191 general practitioners, 129 of which had been randomly sampled. Questions concerned primary prevention (tobacco, alcohol, diet, exposure to sunlight, occupation) and cancer screening (uterine cervix, breast, colo-rectum, prostate, other cancers). In addition, physicians were also interviewed on difficulties encountered in their practice, and about their initial and further medical training in this field. The response rate was high (85%). According to doctors' responses, smoking prevention is the best defined primary prevention strategy, unlike alcohol prevention and advice on diet with which physicians seem to have more difficulty. We noted a great diversity for screening, even for cancers for which a consensus on screening exists (uterine cervix, breast). For cancers of the colon and prostate, the interviewed physicians report screening on a wide scale but in many different ways. Analysis of the factors explaining these variations and non-compliance with existing recommendations seems to be necessary as well as studies comparing in this specific field our results with the actual practices of doctors. This will allow the implementation of well organised, well targeted and efficient primary prevention and screening in which the role of the general practitioner is clearly defined.