Thirty-four children (36 diseased hips and 32 contralateral normal hips) under treatment for Legg-Calve'-Perthes Disease had arthrography. True contour of the femoral head and acetabulum, congruity of the hip joint was observed. We calculated sphericity of the femoral head by Caput index, lateral subluxation by migration index and medial joint space widening. In normal hip, the contour of the femoral head was completely spherical. Femoral head of LCPD was more flattened in coronal (A P projection) than in sagittal plane (frog leg projection). Arthrogram was not more accurate than plain film in determining degree of lateral subluxation. Arthrogram was very helpful to observe congruity of the hip joint and its most congruous position and to detect and confirm hinge abduction.