Research in developmental and behavioral pediatrics is characterized by special methodological problems involving measurement, design, and analysis related to research questions, populations, and nature of interventions in this field. To sensitize researchers and practitioners to these problems and to enhance the quality of research and critical consumption of research reports, this special issue provides a summary of basic methodological issues in developmental and behavioral pediatrics. Advances in this field will require the kind of critical observation and decision making that are shared by researchers and practitioners and are illustrated by contributions to this issue.