Twenty computed tomographic (CT) scans of infants in spica casts after closed or open reduction for developmental hip dislocation (DDH) were analyzed for intra- and interrater reliability. Ten measurements of infant hip anatomy were assessed by three raters by using standard statistical analysis. All six measurements of acetabular anteversion and lateral or posterior displacement of the femoral metaphysis from the acetabulum or from a modified Shenton's line drawn from the pubic rami demonstrated both intra- and interrater reliability. All four measurements of acetabular structure could not be reliably measured either within or between observers. We also introduced a new measurement based on the principle of Shenton's line to aid in the assessment of femoral-head location after reduction in patients with DDH; this was reliably determined both within and among observers.