BACKGROUND. Although primary care physicians are responsible for providing follow-up care after a positive newborn screen, little is known about their willingness or ability to do so. METHODS. A national mail survey of a random sample of 350 general pediatricians and 350 family physicians was conducted from April to June 2006. RESULTS. The response rate was 63% among pediatricians and 50% among family physicians. Most pediatricians (89.7%) and nearly one half of family physicians (44.1%) had had a patient with a positive newborn screen within the past 5 years. Most respondents thought that primary care physicians should be responsible for informing families about a positive newborn screen (73.2%), arranging confirmatory testing (66.0%), and coordinating subspecialty referral (85.3%). However, more than one half (56.2%) would prefer newborn screening programs to provide the initial evaluation of positive newborn screening results. Some respondents ( but fewer pediatricians than family physicians) reported that they were not competent to discuss conditions included in newborn screening panels (eg, 22.6% of pediatricians and 53.2% of family physicians for phenylketonuria and 8.8% of pediatricians and 40.4% of family physicians for congenital hypothyroidism). More than one half (58.3%) thought that families with a child diagnosed as having congenital hypothyroidism should receive formal genetic counseling. Respondents were less likely to think that families with a child with sickle cell trait, compared with families with a child who is a cystic fibrosis carrier, should receive formal genetic counseling (69.3% vs 84.1%). CONCLUSIONS. Many primary care physicians are not prepared to manage the follow-up care of children with a positive newborn screen, including initial counseling, diagnosis, and subspecialty referral. New strategies are needed to ensure appropriate and equitable health care delivery.