Where does hematology end and oncology begin? Questions of professional boundaries and medical authority.

This article recounts the development of the American Society of Clinical Oncology (ASCO) and explores the role of its members in defining oncology's boundaries-boundaries dictated by scientific innovations, major changes in the structure of medical specialization, and the competing efforts of closely related professional groups. Oral histories, journal articles, and unpublished materials from the ASCO History of Oncology Archive were reviewed to analyze these events closely. In 1972, the American Board of Internal Medicine recognized medical oncology as a subspecialty, creating tensions between oncology and hematology as each discipline defended its identity. Drawing on sources produced by hematologists, historian Keith Wailoo (Wailoo, Drawing Blood, 1997) has shown that when medical oncologists claimed wide-ranging expertise over the treatment of all patients suffering from malignant disease in their pursuit of specialty status, the leukemias became contested ground. This article extends this thesis by reviewing the central role of ASCO in these events and recreating the dialogue between members of the two fields as they sought recognition at individual institutions and, more broadly, within American medicine. By acknowledging the contestation of its authority and the results of these prolonged negotiations, we can better understand the current status of oncology and its future outlook.