QUESTION UNDER STUDY: Physicians play a key role in motivating women to undergo mammography screening. In 1998 we assessed Swiss physicians' attitudes to mammography screening and their prescription behaviour in this regard. METHODS: All female physicians and every second male physician aged 50-69 who were either not board-certified or board-certified in general practice, internal medicine, or obstetrics/gynaecology were sent a questionnaire. The response rate was 50% and thus 738 questionnaires were included in this study. Of the study population 39% were female and 61% male physicians. The distribution of professional backgrounds was: 27% board-certified general practitioners; 23% board-certified internists; 11% board-certified gynaecologists; 39% not board-certified. RESULTS: 55% of all study participants were in favour of a mammography screening programme for women aged over 50 in Switzerland, but breast self-examination and clinical breast examination were judged to have a more positive impact on breast cancer survival. Among clinically practising physicians, 22% reported generally prescribing biannual screening mammographies for women aged 50-69. Irrespective of other determinants, physicians from the Italian- and French-speaking parts of Switzerland prescribed screening mammographies more often than their colleagues from the German-speaking part (odds ratio [OR] 2.5; 95% confidence interval [CI] 1.5-4.2). Clinical practice in obstetrics/gynaecology (OR 2.4; CI 1.3-4.2) and a self-reported high level of knowledge concerning mammography screening (OR 1.9; CI 1.1-3.2) were also positively associated with the prescription of screening mammography. CONCLUSIONS: Since mammography screening programmes exist in only three French-speaking cantons of Switzerland (VS; VD; GE), the gap in prescription of screening mammographies between French/Italian- and German-speaking regions must be narrowed to prevent a higher prevalence of side effects from opportunistic screening among German-speaking women. There is a need to educate physicians and the political community regarding the risks and benefits of mammography screening.