Two related techniques of breast epithelial sampling have emerged in the past several years: ductal lavage, in which fluid-yielding nipple ducts are cannulated at their orifices and lavaged with saline while the breast is intermittently massaged; and ductoscopy, in which discharging or fluid-yielding duct orifices are dilated, intubated with a microendoscope, and the lumen directly visualized. Both of these techniques have significant potential in terms of allowing the repeated sampling of ductal epithelium over time and, as such, have generated considerable enthusiasm. However, data regarding the impact of these techniques on the detection of significant breast disease is very scant. It is important at the outset of the assessment of this new technology that breast cancer clinicians and clinical researchers think carefully about the standards of evidence that need to be met regarding the benefits of these procedures before they are widely adopted. In this review of the rationale and early results of these procedures, we attempt to define some of these evidentiary requirements.