Applying the methods and tools of outcomes research, "evaluation of the impact of health care on the health outcomes or 'end results' of patients and populations," to the clinical domain of emergency services for children offers an important strategic opportunity for addressing the questions that confront all health care services: What works? For which patients? At what cost? From whose perspective? Although the important questions to address are extensive, much of the intersection between emergency services and outcomes research remains unexplored. Important challenges for researchers intrigued by the opportunities at this intersection of fields include: 1) clear definition of the scope of emergency services; 2) consideration of the appropriate end-point of emergency services-the entire episode of illness and/or services provided within the emergency setting; 3) selection and development of measures that incorporate children's and families' perspectives; and 4) a clear focus on linking research findings with strategies for improving outcomes and informed decision making. This essay will provide an overview of accomplishments and challenges from the field of outcomes research, suggest important opportunities for applying existing methods to emergency medical services for children, and identify potential career paths for current and future investigators.