Textbook accounts of this subject are inadequate. This review considers the work of Cooper and Salmon and reproduces some of their figures. Applications in the diagnosis and treatment of cancer are discussed. The largest mammary arteries are the lateral (from the axillary) and the anterior medial and posterior medial (from the internal thoracic). The branches of these arteries do not follow the duct system, but instead form a plexus in the anterior fat layer. Normally there are no hypervascular or hypovascular areas. The contribution of the mammary branches of the posterior (aortic) intercostal arteries is minor. There are superficial and deep sets of veins, the latter associated with arteries. Mammary vessels of living women are demonstrated by infrared photography, thermography, and mammography. In the diagnostic use of these methods there is a tendency to rely upon the concept of normal vascular symmetry, but this is a fallacy.