This study was undertaken to describe subspecialty characteristics and practices of the population of pediatricians given the ongoing controversy regarding a projected manpower oversupply of general pediatricians. A questionnaire was mailed to a national random sample of 1620 United States physicians listed in the American Medical Association's Physician Masterfile as being in office-based pediatric practice. The final response rate was 63%. Seventy percent of respondents designated their practices as "general pediatrics" versus 17% as "general pediatrics with a specific subspecialty interest" and 13% as "subspecialty practice." The general pediatricians with a specific subspecialty interest were intermediate in the proportion that had some training in a pediatric fellowship program (general pediatricians with a specific subspecialty interest, 63% versus general pediatricians, 14%, P < .0001, and pediatricians with a subspecialty practice, 92%, P < .0001) and that were certified in a pediatric subspecialty by the American Board of Pediatrics (general pediatricians with a specific subspecialty interest 16% versus general pediatricians, 2%, P < .0001, and pediatricians with a subspecialty practice, 62%, P < .0001). They were also intermediate in the proportion involved in various academic pursuits. Their practices, however, more closely resembled general pediatricians than pediatricians with a subspecialty practice in their location, setting, associates, and commitment to primary care. They were more likely than general pediatricians to utilize or provide specialized tests or procedures. A large percentage of pediatricians incorporate subspecialty elements into their general pediatric practices. Models of current and projected pediatric manpower supply need to be reassessed in light of this form of practice.