OBJECTIVES: In Brazil, according to the National Cancer Institute (INCA, 2005), approximately 50% of all breast cancer (BC) diagnosis point to advanced cases at the time of first presentation (stages III and IV), which results in a maximal 5 year survival rate of 36% for these women (The Susan G. Komen Breast Cancer Foundation). It is supposed that this mortality could be reduced through an improvement of public breast health care to encourage early detection of breast lesions for the population. Hence, the Associação Hospitalar Moinhos de Vento started a partnership with Health Secretary of Porto Alegre (capital of Rio Grande do Sul State) to perform a study to measure the impact of annual clinical examinations together with mammography for underserved women over 40 years old. METHODS: A total of 9,218 women aged between 40 and 69 year old, living in a delimited geographic area connected to 18 Health Care Units of Porto Alegre are being studied; BC risk factors are also being assessed. For these, yearly clinical examinations and screening mammograms are performed. The analysis is related to the first four years of the project. Its results are compared against INCA epidemiologic data. RESULTS: Among the searched universe, 50 women have been diagnosed for BC. Comparing the cancer staging of these women at diagnosis with INCA data for the same region, we have: stage 0 (16% VS 6.7%), stage I (38% VS 20.6%), stage II (32% VS 45%), stage III (10% VS 20%) and stage IV (4% VS 7.7%), respectively. CONCLUSIONS: The study showed that the annual screening associated with preventive mammography for women above 40 year old increased their likelihood of an early diagnosis of BC, thus yielding them a better survival and cure prognostic. Therefore, the national adoption of this protocol could reduce the high mortality associated with this neoplasia.