By virtue of their ongoing relationship with families and young children, pediatric primary care providers are well positioned to participate in the early detection of children's behavioral, developmental, and psychosocial problems. Yet research suggests that many such problems elude early detection. Awareness of the prevalence of such problems should encourage pediatric providers to carefully elicit parents' opinions and concerns, obtain a relevant behavioral and developmental history, skillfully observe parent and child behaviors, and obtain, when indicated, the opinions of such other relevant professionals as preschool teachers. Possible strategies to improve early detection include the use of parent questionnaires, parent record-keeping of children's behavior, and a developmental screening tool as an aid to surveillance. The development of a classification system for such problems designed for primary care, rather than psychiatry, should also facilitate early detection.