Sentinel lymph node biopsy in women with breast cancer has become routine in many surgical practices; yet basic questions regarding the procedure remain unanswered. The National Surgical Adjuvant Bowel and Breast Project (NSABP) and the American College of Surgeons Oncology Group (ACOSOG) trials address the issues of morbidity, efficacy, safety, and the significance of low-volume disease. NSABP B-32 randomizes women to sentinel lymph node biopsy followed by a standard level I and II axillary dissection or sentinel lymph node biopsy without dissection unless metastatic disease is noted by H&E examination. Overall survival, disease-free survival, and morbidity serve as end points. Further pathologic evaluation of the lymph nodes with immunohistochemistry will be performed by the study center. This study is nearing its anticipated accrual goal. Patients enrolled in the now-closed ACOSOG Z0010 trial underwent bone marrow aspiration just prior to sentinel node biopsy. Immunocytochemical analysis of the marrow will be compared to sentinel lymph node (SLN) biopsy to determine prognostic accuracy. ACOSOG Z0011 randomizes women undergoing breast-conserving therapy with low-volume axillary disease to completion axillary dissection or observation. Overall survival, disease-free survival, local regional control, and morbidity serve as end points. This trial is currently enrolling patients.