OBJECTIVES: Although breast cancer is highly prevalent and the third leading cause of mortality for women in Europe, little is known about treatment patterns for women with this disease. Intra- or cross-country comparisons of treatment patterns are difficult due to the absence of automated data systems that capture clinical or health care claims records for representative population samples. To overcome this barrier, we designed and developed a web-based study to determine patterns of care in advanced stage breast cancer for France, England, Italy, Spain, and Germany. METHODS: The study includes three components: 1) survey design and validation; 2) web-translation of the survey; and 3) identification and recruitment of physicians to complete the survey. Survey Design: Country-specific and international treatment guidelines were collated into a comprehensive list of management strategies. The survey is grouped into categories: Initial evaluation; initial therapy; second and third-line treatment; monitoring; supportive care. Web Translation: The web site is designed to elicit specific answers rather than open responses. Drop down lists and check boxes facilitate completion. "Yes" answers to specific questions ("Chemotherapy is indicated: Yes/No") direct the respondent to more detailed questions on the topic. Respondents log in with a secure ID/password, and can enter and exit as many times as is needed. Physician Recruitment: Physician key opinion leaders (KOLs) with expertise in breast cancer are recruited from each country (stratified by service area) in three separate phases. RESULTS: In Phase I, KOLs review the "beta" web site, offering suggestions for improving its accuracy and comprehensiveness. In Phase II, a new group of KOLs complete the survey from their home or office. In Phase III, KOLs from Phase I review the summary results and comment on the findings. CONCLUSIONS: Although subject to certain limitations, the web-based survey offers an efficient strategy to determine practice patterns for advanced breast cancer.