Medical practitioners in the 1920’s and 1930’s saw ultrasonography as a therapeutic tool and utilized it to treat soft-tissue injuries. Early industrial applications were diagnostic; it was used to detect flaws in materials. During World War II, major technical advances in the propagation, receipt, and processing of sound waves resulted from the military’s work in sonar and radar, which are also based on the principle ofecho’3. In the 1950’s, crude imaging studies of the fetus during pregnancy provided physicians with the first indication of the potential of ultrasonography for as- sessing soft-tissue structures in the body. In the 1960’s and 1970’s, ultrasonography gained wide acceptance as an imaging technique for many organs in the body. Because the ultrasound beam does not penetrate bone and the resolution of soft-tissue structures was relatively poor, ultrasonography seemed to have no advantages com- pared with other techniques that were available to the orthopaedic surgeon. In the 1970’s, a few orthopaedists recognized the potential of ultrasonography for orthopaedic conditions and actually explored the use of static-imaging equipment to study patellar tracking and injury to the rotator cufF. In Austria, the pediatric orthopaedic surgeon Graf began the first in-depth use of ultrasonography to evaluate the hip in infants’5. His initial work was done with a B- scan unit, in which the transducer is attached to an articulated arm that controls movement. Graf believed that abnormal position of the hip could be determined by evaluation of the surface contour of the pelvis and the proximal part of the femur. During these studies, it became apparent that the ultrasound beam would pass through cartilage and that it was possible to evaluate the anatomy of the developing hip joint in detail. Improvements in ultrasound equipment fostered greater interest in ultrasonography of the hip. Real-time equipment, in which the ultrasound image changes quickly enough to permit observation of motion, facilitated examination in multiple planes. In the United States, Novick et al. and a Alfred I. duPont Institute, P.O. Box 269, 1600 Rockland Road, Wilmington, Delaware 19899. Please address requests for reprints to Dr. Harcke, Department of Medical Imaging. Harcke et al.2’ began investigating the hip in the infant using a multiplanar approach that differed from the method proposed by Graf. During the 1980’s, the number of reports on the use of ultrasound examination to diagnose and man- age congenital problems of the hip increased annually. In Europe, ultrasound examination of the hip is done by orthopaedists, radiologists, and even some pediatricians, and a large number of patients have been examined. Ultrasonography of the hip has developed more slowly in the United States, and most examinations are performed by radiologists working in association with orthopaedists. This review examines the current use of ultrasound examination in the diagnosis and management of congenital dislocation and dysplasia of the hip. As experience has grown, it has become evident that ultrasonography has distinct advantages compared with other imaging techniques. There is not yet agreement, however, on how or if the orthopaedist should incorporate ultrasonography into current practice. We want to point out the strengths of ultrasound examination and to indicate how it has been used successfully at our institution. New and as yet unanswered issues concerning technique, screening of the hip in newborns, and protocols for treatment are addressed.