We thank Joseph Flaherty, MD, Robert Reece, MD, and Emily Wood for their support and the following members of the Pediatric Practice Research Group who participated in this study: Associated Pediatricians, Valparaiso, Ind; Child Life Center, Homewood, Ill; Winfield-Moody Health Center, Chicago, Ill; Child and Adolescent Health Associates, Chicago; Traisman, Benuck, Traisman, & Merens, Evanston, Ill; Lake Forest Pediatrics, Lake Forest, Ill; DuPage Pediatrics, Darien, Ill; Glenbrook Pediatrics, Glenview, Ill; Pediatric Specialists, Barrington, Ill; North Arlington Pediatrics, Arlington Heights, Ill; Northwestern University Medical Faculty Foundation, Chicago; Infant Welfare Society, Chicago; Arnulfo Delgado, MD, Chicago; Children's Healthcare, Chicago; Children's Primary Care Services, Chicago; and Pediatric Associates of Barrington SC, Barrington.