Transpelvic CT was used to quantify the relationship between the acetabulum and proximal femur in 21 adult patients (33 hips) with congenital hip dysplasia (defined by a center edge angle of <20°). The anterior and posterior acetabular sector angles (AASA and PASA) were measured, as well as the degree of acetabular and femoral anteversion. The results demonstrated deficient anterior acetabular support (i.e., decreased AASA) in –two-thirds of the dysplastic hips and reduced posterior support (i.e., decreased PASA) in one-third. The acetabular anteversion was normal. The femoral anteversion, however, was greater than normal in most hips. As important additional information is obtained by CT compared with conventional radiography, CT is recommended when operative procedures aimed at preventing or postponing osteoarthrosis are considered.