In Health Services Research, Guy David and colleagues evaluate whether patient-centered medical homes (PCMHs) reduce emergency department (ED) visits among patients with and without chronic conditions. The authors use data from approximately 460,000 Independence Blue Cross patients enrolled in 280 primary care practices, all of which converted to PCMH status between 2008 and 2012. PCMH certification was associated with a 5-8% reduction in ED visits among a practice's chronically ill patients, but had no effect on patients without chronic medical conditions. These findings were robust to a number of specifications, including analyzing avoidable and weekend ED visits alone. The largest reductions in ED visits were concentrated among patients with diabetes and hypertension. The authors conclude that any reduction in ED utilization is likely to be the result of better management of chronic illness, rather than expansion of access to primary care clinics.