An acetabular cup prosthetic device comprised of an outer shell component and a inner bearing insert and the method of implanting the acetabular cup prosthetic within a patient. The outer surface of the shell component for the present invention acetabular cup has a plurality of regions which conform to the curvature of at least one ellipsoid. To implant the shell component, the acetabulum of a patient is spherically reamed to a size slightly smaller than that of the outer surface of the shell component. As the shell component is inserted into the spherically shaped acetabulum, the interior surface of the acetabular cavity deforms to assume a substantially ellipsoidal curvature, producing an interference fit between the rim region of the shell component and the upper peripheral rim region of the acetabulum. The remaining surface regions of the acetabulum conform substantially to the ellipsoidal shape or shapes defined by the remaining surface regions of the shell component so that surface contact is established without the development of ejection forces therebetween.