OBJECTIVE: To assess the impact of chronic conditions on children's emergency department (ED) use. STUDY DESIGN: Retrospective analysis of 1 850 027 ED visits in 2010 by 3 250 383 children ages 1-21 years continuously enrolled in Medicaid from 10 states included in the Truven Marketscan Medicaid Database. The main outcome was the annual ED visit rate not resulting in hospitalization per 1000 enrollees. We compared rates by enrollees' characteristics, including type and number of chronic conditions, and medical technology (eg, gastrostomy, tracheostomy), using Poisson regression. To assess chronic conditions, we used the Agency for Healthcare Research and Quality's Chronic Condition Indicator system, assigning chronic conditions with ED visit rates >/=75th percentile as having the "highest" visit rates. RESULTS: The overall annual ED visit rate was 569 per 1000 enrollees. As the number of the children's chronic conditions increased from 0 to >/=3, visit rates increased by 180% (from 376 to 1053 per 1000 enrollees, P < .001). Rates were 174% higher in children assisted with vs without medical technology (1546 vs 565, P < .001). Sickle cell anemia, epilepsy, and asthma were among the chronic conditions associated with the highest ED visit rates (all >/=1003 per 1000 enrollees). CONCLUSIONS: The highest ED visit rates resulting in discharge to home occurred in children with multiple chronic conditions, technology assistance, and specific conditions such as sickle cell anemia. Future studies should assess the preventability of ED visits in these populations and identify opportunities for reducing their ED use.