Ultrasound imaging has been used extensively to detect abnormalities of the non-lactating breast. In contrast, the use of ultrasound for the investigation of pathology of the lactating breast is limited. Recent studies have re-examined the anatomy of the lactating breast highlighting features unique to this phase of breast development. These features should be taken into consideration along with knowledge of common lactation pathologies in order to make an accurate diagnosis when examining the lactating breast. Scanning techniques and ultrasound appearances of the normal lactating breast will be contrasted to those of the non-lactating breast. In addition ultrasound characteristics of common pathologies encountered during lactation will be described.