A new field, termed emergency ultrasound (EUS), has recently been established. The past decade saw rapid development in the field of EUS in adult patients, especially as performed by emergency medicine physicians. Ultrasound imaging offers several advantages over traditional radiographic techniques, many of which are especially relevant to patients in the pediatric emergency department. Recent literature has documented increased use of EUS for pediatric patients. This review will examine basic principles of ultrasound relevant to pediatric emergency medicine physicians. Emphasis will be placed on understanding the instrument and its limitations. In addition, we will review recent developments in this field. It is our goal that the reader will gain an understanding of the strengths and limitations of this instrument and will therefore be in a position to plan their own program in EUS in pediatrics. Furthermore, it is hoped that this review will serve as an impetus for innovative research, to refine and extend the indications of this modality to benefit patients in the pediatric emergency department.