Background: We assessed trends in incidence, in-hospital mortality, and admission among patients with adult congenital heart disease (ACHD) presenting to the emergency department (ED) from 2006 to 2012. Hypothesis: There is a considerable burden of ACHD in the US EDs. Methods: We used the 2006-2012 US Nationwide Emergency Department Sample. All ED visits with ACHD were identified using standard International Classification of Diseases, Ninth Edition, Clinical Modification codes. Results: The number of patients presenting to the ED with simple (40.6%) as well as complex (37.6%) ACHD across 2006-2012 increased significantly. Also, there was a considerable increase in prevalence of traditional cardiovascular risk factors among ACHD patients, including hypertension, diabetes, smoking, obesity, and chronic kidney disease. Besides miscellaneous noncardiovascular conditions, nonspecific chest pain (15.9%) and respiratory disorders (15.0%) were the most common reasons for ED visits among patients with simple and complex ACHD, respectively. Although there was a trend toward decrease in admissions across 2006-2012 (P trend < 0.001), the proportion of patients with ACHD presenting to ED requiring admission remained substantial (63.4%). Finally, there was significant variation in admission trends across different geographic locations, hospital types, insurance status, and ED volume among ACHD patients presenting to the ED. Conclusions: There has been a progressive increase in number of ED visits among ACHD patients across 2006-2012 in the United States. Moreover, the cardiovascular risk-factor profile of ACHD patients has changed, adding to complexity in management. Current health care delivery to ACHD patients also shows significant geographical, hospital-based, and insurance status-based disparities.