In the Journal of Adolescent Health, Alexander Bain and colleagues, including Charlene Wong, Daniel Polsky, Raina Merchant, and David Rubinm, identify the most prevalent and costly inpatient hospitalizations in a national cohort of privately insured young adults since the implementation of the Affordable Care Act. The researchers analyzed 158,777 hospitalizations among 4.7 million young adults from January 2012 to June 2013. They find that the top diagnoses for young adult female hospitalizations were pregnancy related (71.9%) and mental illness (8.9%). The top diagnoses for young adult male hospitalizations were mental illness (39.3%) and injuries and poisoning (14.0%). Mean and median total out-of-pocket costs for any young adult hospitalizations were $1,034 and $700, respectively. The most expensive out-of-pocket hospitalizations were for dermatologic diseases. This study establishes a baseline for ongoing assessment of inpatient utilization and out-of-pocket cost for privately insured young adults in the United States, and helps inform health care priorities for the most common and costly diseases that require hospitalization among young adults.