Cancer is an important disease, and health care services have the potential to improve the quality and quantity of life for cancer patients. The delivery of these services also has recently been well codified. Given this framework, cancer care presents a unique opportunity for clinicians to develop and test outcome measures across diverse practice settings. Recently, the Institute of Medicine released a report reviewing the quality of cancer care in the United States and called for further development and monitoring of quality indicators. Thus, as we move into the 21st century, professional and regulatory agencies will be seeking to expand process measures and develop and validate outcomes-oriented measures for cancer and other diseases. For such measures to be clinically relevant and feasible, it is key that the oncology community take an active leadership role in this process. To set the stage for such activities, this article first reviews broad methodologic concerns involved in selecting measures of the quality of care, using breast cancer to exemplify key issues. We then use the case of breast cancer to review the different phases of cancer care and provide examples of phase-specific measures that, after careful operationalization, testing, and validation, could be used as the basis of an agenda for measuring the quality of breast cancer care in oncology practice. The diffusion of process and outcome measures into practice; the practicality, reliability, and validity of these measures; and the impact that these indicators have on practice patterns and the health of populations will be key to evaluating the success of such quality-of-care paradigms. Ultimately, improved quality of care should translate into morbidity and mortality reductions.