This study, which has been prompted by the evidence of confusion and the divergence of opinion among clinicians and pathologists alike as to the nature of so-called "Paget's disease of the breast," embraces a thorough review of 29 cases1 as well as a review of studies and observations by other investigators of this malady. The origin of this dissension emanates from confusion in regard to the cause and the significance of (and, consequently, the therapy indicated for) "Paget's disease." Here an attempt is made to answer the following questions: 1. What is "Paget's disease of the breast"? 2. Is there any cogent evidence as to its etiologic derivation? 3. How should it be treated? 4. Does the name "Paget's disease," which this malady has come to bear, actually clarify or confuse the picture, and is it, therefore, a justifiable eponym? HISTORY In 1874, Sir James Paget recorded in St.