The extant nomenclature for single ventricle (SV) hearts is reviewed for the purpose of establishing a unified reporting system. The subject was debated and reviewed by members of the STS-Congenital Heart Surgery Database Committee and representatives from the European Association for Cardiothoracic Surgery. Efforts were made to include all relevant nomenclature categories using synonyms where appropriate. Although many issues regarding single ventricle or univentricular hearts remain unresolved among anatomists and pathologists, a classification is proposed that is relevant to surgical therapy. A comprehensive database set is presented, which is based on a hierarchical scheme. Data are entered at various levels of complexity and detail, which can be determined by the clinician. These data can lay the foundation for comprehensive risk stratification analyses. A minimum data set is also presented that will allow for data sharing and would lend itself to basic interpretation of trends. Outcome tables relating diagnoses, procedures, and various risk factors are presented.