Public interest in the performance of pediatric cardiac surgery programs is increasing. Mortality is the focus of outcomes reporting in pediatric cardiac surgery due both to its importance as an outcome and its accessibility in clinical and administrative data. However, assessment of mortality rates in congenital cardiac surgery is more complex than in adult cardiac surgery due to the wider range of procedures performed and the low frequency at which each individual procedure is performed. In order to accurately describe mortality, one must understand types of databases, data definitions, and risk adjustment methods. We review the risk adjustment methodologies and data sources used to produce mortality statistics. In addition, the issues of data quality and defining mortality are discussed.