An understanding of stiffness characteristics of different body regions, such as thorax, abdomen and pelvis of ES-2re and SID-IIs dummies under controlled laboratory test conditions is essential for development of both compatible performance targets for countermeasures and occupant protection strategies to meet the recently updated FMVSS214, LINCAP and IIHS Dynamic Side Impact Test requirements. The primary purpose of this study is to determine the transfer functions between the ES-2re and SID-IIs dummies for different body regions under identical test conditions using flat rigid wall sled tests. The experimental set-up consists of a flat rigid wall with five instrumented load wall plates aligned with dummy's shoulder, thorax, abdomen, pelvis and femur/knee impacting a stationary dummy seated on a rigid low friction seat at a pre-determined velocity. The relative location and orientation of the load wall plates are adjusted relative to the body regions of the ES-2re and SID-IIs dummies respectively. The load wall forces and dummy responses are evaluated by varying four different test parameters to investigate the effects of velocity (initial velocity vs. velocity-time pulse), shoulder engagement (with and without shoulder loadwall plate), initial arm position of the dummy (40 deg. vs. 90 deg), and oblique loading of thorax by rotating the thorax loadwall plate by 15 deg. Cause-and-effect relationships between the input loading conditions and dummy responses are established using linear regression analysis for both the dummies. Subsequently, the transfer functions are developed to establish relationships of responses between the two dummies for each body region. The usefulness of these transfer functions is discussed, and demonstrated.