Family physicians treat an increasing number of children with metabolic disorders identified through newborn screening, and they are often the first line of defense in responding to an abnormal screening result. How the family physician chooses to interpret information from the screening and what he or she chooses to tell the family affects the parent-child relationship, as well as the infant's medical and developmental outcomes. Family physicians must, therefore, be familiar with the current state of expanded newborn screening to effectively communicate results and formulate interventions. They also must recognize signs of metabolic disorders that may not be detected by newborn screening or that may not be a part of newborn screening in their state. For every infant identified with a metabolic disorder, 12 to 60 additional infants will receive a false-positive screening result. One recommendation for communicating results to parents is to explain what the initial and follow-up findings mean, even if the diagnosis is not confirmed. For infants with true-positive results, long-term follow-up involves regular medical examinations, communication with a metabolic treatment center, and developmental and neuropsychological testing to detect possible associated disorders in time for early intervention. This article provides a description of metabolic disorders included in expanded newborn screening programs; a list of disorders screened for in each state; and resources for obtaining ACTion sheets (guidelines for responding to newborn screening results), fact sheets, and emergency and acute illness protocols.