The rear cross-car stiffener subsystem is generally located at the underside of the rear compartment pan of a car body and connects the two rear longitudinal rails or rear rockers. The primary purpose of this subsystem is to maintain structural integrity as well as fuel system integrity in a rear angle impact or dynamic side impact collision.To evaluate the effect of this subsystem on lateral crashworthiness in a high speed angle impact, a finite element model consisting of the cross-car bar, a portion of rear compartment pan and both rear rails was developed and analyzed with the DYNA3D crashworthiness simulation software. Thus, the cross-car stiffener subsystem design including the welding pattern was finalized and the acceptable design was successfully implemented in the vehicle. Subsequently drop silo tests were carried out to further verify the design and to improve the manufacturing process.In this paper it is demonstrated that the design, analysis and development process of a cross-car stiffener subsystem was successfully accomplished with the design of a cross-car member and suitable spot welds arrangement without undergoing a full scale angle impact vehicle test. Furthermore, many welding patterns between this member and the underbody and rear rails were studied through DYNA3D analysis and later through inexpensive drop silo tests.