The breast is a relatively clean organ comprised of skin, fatty tissue, and mammary glandular elements that have no direct connection to any major body cavity or visceral structures. In the absence of concurrent major reconstruction, breast surgery generally is not accompanied by large-scale fluid shifts, infectious complications, or hemorrhage. Thus, most breast operations are categorized as low-morbidity procedures. Because the breast is the site of the most common cancer afflicting American women, however, a variety of complications can occur in association with diagnostic and multidisciplinary management procedures. Some of these complications are related to the breast itself, and others are associated with axillary staging procedures. This article first addresses some general, nonspecific complications (wound infections, seroma formation, hematoma). It then discusses complications that are specific to particular breast-related procedures: lumpectomy (including both diagnostic open biopsy and breast-conservation therapy for cancer), mastectomy; axillary lymph node dissection (ALND), lymphatic mapping/sentinel lymph node biopsy, and reconstruction. Complications related to reconstruction are discussed in a separate article in this issue. General wound complications related to breast and axillary surgeryBecause it is a peripheral soft tissue organ, many wound complications related to breast procedures are relatively minor and frequently are managed on an outpatient basis. It therefore is difficult to establish accurate incidence rates for these events. As discussed later, however, reported studies