Interpreting the Volume-Outcome Relationship in the Context of Cancer Care is a summary of a workshop held on May 11, 2000, which brought together experts to review evidence of the relationship between volume of services and health-related outcomes for cancer and other conditions, discuss methodological issues related to the interpretation of the association between volume and outcome, assess the applicability of volume as an indicator of quality of care, and identify research needed to better understand the volume--outcome relationship and its application to quality improvement.