Although most U.S. children live within an hour's drive of a pediatric subspecialist, such care is less widely available in certain regions and for certain subspecialties. According to this study, the average distance to a subspecialist ranged from 15 miles for neonatology to 78 miles for pediatric sports medicine. Fewer than one-half of hospital referral regions had a provider for 7 of 16 pediatric subspecialties, suggesting that the supply of pediatric subspecialties is inadequate, pediatric subspecialists are distributed inequitably, or the market for pediatric subspecialists exceeds the hospital referral regions. Mayer, Pediatrics 118(6):2313-2321, 2006 (AHRQ Grant HS13309).