We searched MEDLINE to identify all English-language articles using original US data published in the content areas of interest between January 1, 1992, and December 31, 2002. Because prevailing wisdom on the adequacy of physician supply changes frequently, we selected a narrow and recent time frame for the review. The articles identified for this study were found in a larger search of articles related to the availability and quality of pediatric subspecialty care that required all retained articles to fall into one or more of the following categories: (1) pediatric subspecialty workforce, (2) the role of insurance in use of pediatric subspecialty care, and (3) comparisons of pediatric subspecialists with general pediatricians and/or adult subspecialists in terms of knowledge, practices, or outcomes. Only articles on the pediatric subspecialty workforce are relevant for the present review. Inconsistencies in Medical Subject Heading term assignment required use of an exhaustive list of Medical Subject Heading terms to identify articles. The first level of Medical Subject Heading terms used included the following: medical specialties (allergy and immunology, anesthesiology, dermatology, emergency medicine, internal medicine [cardiology, endocrinology, gastroenterology, hematology, medical oncology, nephrology, pulmonary disease {specialty}, and rheumatology], neonatology, neurology, pediatrics [neonatology], and radiology), surgical specialties (colorectal surgery; neurosurgery; ophthalmology; otolaryngology; surgery; surgery, plastic; thoracic surgery; and urology), and psychiatry. All articles were cross-referenced with pediatrics, infant, child, and adolescent. Other Medical Subject Headings or keywords cross-referenced included the following: comparative study, managed care, health services accessibility, manpower, health maintenance organizations, insurance, physician practice patterns, referral and consultation, workforce, developmental pediatrics, and behavioral pediatrics. We also reviewed references of articles for overlooked articles, and included 2 Future of Pediatric Education (FOPE) project II articles published in 2003. (The FOPE project II was a 3-year grant-funded effort of the pediatric community to assess the future of the pediatric workforce. As part of this effort, 17 subspecialties participated in the Survey of Sections Project between March 1997 and October 1998.)