Physicians concerned with children's diseases are well aware of the many difficulties in the diagnosis and treatment of disorders of infant joints. Part of the problem is our present inability to obtain a radiograph of the portion of the joint which is cartilaginous, the cartilaginous epiphysis being generally invisible. In adults, when a bone is ossified up to the articular cartilage it is hard enough to diagnose dislocation, subluxation, or reduction of a joint. In an infant with bone composed of radiographically invisible cartilage for an inch around the joint, it is that much more difficult. Because an infant's hip joint is roentgenographically invisible, it is necessary to draw lines and angles on the bony parts to determine if the hip is properly seated. Many times these signs are unreliable, and Caffey et al. (1) recently raised serious doubt whether measurements on the bony acetabulum indicate if the cartilaginous acetabulum is normal. At present, the most suitable implement for the correct diagnosis of infant joint disease is arthrography, which is associated with several technical and surgical problems. If it were possible to devise a convenient method for clearly visualizing the outline of the epiphyseal cartilage, correct diagnosis and treatment of congenital dislocation of the hip would be made much easier. This raises the question of whether epiphyseal cartilage has a certain degree of radiographic visibility, and, if so, if there is any practical way of increasing it. That epiphyseal cartilage is visible was suggested by the observation of some shadows on the routine views of infant hips. Examination of any large collection of such films will reveal many with shadows which suggest visualization of the capsule of the joint. Others show within the capsule white shadows which may represent the cartilaginous femoral head. Examples of this are illustrated in Figure 1. These are similar to many of the routine films, but they are considerably brighter because of high-contrast processing. In each of the examples of Figure 1 a large arrow points to a shadow commonly called the capsule. Within this shadow is the ossific center of the femoral head and a less dense area which may represent its cartilaginous portion. It would seem worthwhile to find out what the shadows of Figure 1 are, if there is any way to make them appear more clearly and more regularly, and if any clinical usefulness is to be gained from them. Method To study epiphyseal visibility, the highest contrast was employed. The premise of the study is that epiphyseal cartilage is not invisible on an x-ray film, and that it appears as a different density from the periarticular soft tissues. The theory is that muscle, ligament, tendon, and skin are not opaque to x-rays in the same degree as cartilage, but to a different degree.