A growing body of evidence indicates that certain surgical procedures exhibit a "volume-outcome" relationship in which a higher volume of patients undergoing a particular procedure at a hospital is associated with better outcomes for those patients. The proportion of a hospital's patients operated on by low-volume or less experienced surgeons also may be associated with poor patient outcomes and thus contribute to the hospital "volume-outcome" relationship. This paper analyzes the influence of hospital volume and the proportion of a hospital's patients operated on by low-volume surgeons on patient outcome for 10 procedures, controlling for other selected factors that may influence outcomes. The analysis is based on 503,662 patient abstracts from 757 hospitals. Results indicate that both hospital volume and the proportion of patients operated on by low-volume surgeons are related to quality of care as measured by patient outcomes. Higher hospital volume is positively related to better patient outcomes. These findings are consistent with earlier hospital "volume-outcome" research and add an additional set of procedures using more recent data to the evidence. Unlike previous research on surgeon volume, a positive relationship was found between higher percentage of patients operated on by low-volume surgeons and poorer hospital quality.