Results of the location and recruitment efforts and comparisons of responses from patients who cooperated at different levels in the Second Natural History Study of Congenital Heart Defects are included because they influenced the choice of analytic methods and are essential to the generalizability of the results to the entire study cohort. Included are examination and data collection protocols (e.g., protocol definitions, test procedures, and data editing), statistical methods (e.g., box plots, survival curves, multivariable models, and rate adjustment), participation results (e.g., proportional odds analysis, mortality, location, recruitment, and full participants, including comparison of questionnaire responses and comparison of questionnaire response and physician history), and a discussion.