INTRODUCTION: Mortality has traditionally been perceived as a straightforward measure of outcome and has been used to evaluate surgical performance. In the rapidly developing arena of paediatric cardiac surgery, the insightful analysis of mortality figures is challenging. SOURCES OF DATA: This report discusses the issues involved when mortality is used as a marker for surgical outcome, referring to national and international audit and research data. AREAS OF AGREEMENT: Mortality is an important variable and should be transparently defined, reported and monitored. AREAS OF CONTROVERSY: Definitions of mortality, assessments of risk and interpretations of reported statistics all have limitations that must be recognized. GROWING POINTS: Traditional use of raw early mortality as a simplistic indicator of outcome and performance is evolving to include risk-adjusted mortality, longer-term survival, reinterventions and complications. AREAS TIMELY FOR DEVELOPING RESEARCH: As the vast majority of children undergoing cardiac surgery now survive beyond 30 days, the focus for measures of quality is shifting towards morbidity.