BACKGROUND: Multicenter longitudinal objective data for survival into adulthood of patients who have undergone Fontan procedures are lacking. OBJECTIVES: This study sought to describe transplant-free survival and explore relationships between laboratory measures of ventricular performance and functional status over time. METHODS: Exercise testing, echocardiography, B-type natriuretic peptide, functional health assessment, and medical history abstraction were repeated 9.4 +/- 0.4 years after the Fontan Cross-Sectional Study (Fontan 1) and compared with previous values. Cox regression analysis explored risk factors for interim death or cardiac transplantation. RESULTS: From the original cohort of 546 subjects, 466 were contacted again, and 373 (80%) were enrolled at 21.2 +/- 3.5 years of age. Among subjects with paired testing, the percent predicted maximum oxygen uptake decreased (69 +/- 14% vs. 61 +/- 16%; p < 0.001; n = 95), ejection fraction decreased (58 +/- 11% vs. 55 +/- 10%; p < 0.001; n = 259), and B-type natriuretic peptide increased (median [interquartile range] 13 [7 to 25] pg/mol vs. 18 [9 to 36] pg/mol; p < 0.001; n = 340). At latest follow-up, a lower Pediatric Quality of Life Inventory physical summary score was associated with poorer exercise performance (R2 adjusted = 0.20; p < 0.001; n = 274). Cumulative complications since the Fontan procedure included additional cardiac surgery (32%), catheter intervention (62%), arrhythmia treatment (32%), thrombosis (12%), and protein-losing enteropathy (8%). Since Fontan 1, 54 subjects (10%) have received a heart transplant (n = 23) or died without transplantation (n = 31). The interval risk of death or/cardiac transplantation was associated with poorer ventricular performance and functional health status assessed at Fontan 1, but it was not associated with ventricular morphology, the subject's age, or the type of Fontan connection. CONCLUSIONS: Interim transplant-free survival over 12 years in this Fontan cohort was 90% and was independent of ventricular morphology. Exercise performance decreased and was associated with worse functional health status. Future interventions might focus on preserving exercise capacity. (Relationship Between Functional Health Status and Ventricular Performance After Fontan-Pediatric Heart Network; NCT00132782).