A key determinant of breast cancer outcome in any population is the degree to which newly detected cancers can be diagnosed correctly so that therapy can be selected properly and provided in a timely fashion. A multidisciplinary panel of experts reviewed diagnosis guideline tables and discussed core implementation issues and process indicators based on the resource stratification guidelines. Issues were then summarized in the context of 1) clinical assessment, 2) diagnostic breast imaging, 3) tissue sampling, 4) surgical pathology, 5) laboratory tests and metastatic imaging, and 6) the healthcare system. Patient history provides important information for the clinical assessment of breast and comorbid disease that may influence therapy choices. Focused clinical breast examination and complete physical examination provide guidance on the extent of disease, the presence of metastatic disease, and the ability to tolerate aggressive therapeutic regimens. Breast imaging improves preoperative diagnostic assessment and also permits image-guided needle sampling. Diagnostic mammography was not considered mandatory in low- and middle-income countries when resources are lacking. Needle biopsy is preferred to surgical excision for the initial diagnosis of suspicious breast lesions, unless resources are unavailable. Mastectomy should never be used as a method of tissue diagnosis. The availability of predictive tumor markers, especially estrogen receptor testing, is critical when endocrine therapies are available; quality assessment of immunohistochemistry testing is important to avoid false-negative results. Incremental allocation of resources can help address economic disparities and help ensure equity in access to timely diagnosis. (c)2008 American Cancer Society.