An understanding of the explosive's shock sensitivity is of vital importance for the hazard assessment and vulnerability evaluations of munitions. This paper summarizes the experimental and modeling research relating to shock initiation and sympathetic reaction of PBXN-109. The modeling has focused on developing and applying Ignition and Growth (I&G) models using the hydrocode LS-DYNA, taking into consideration the reduced shock sensitivity due to changes in source of ingredients. Detonation front tracking was applied to selected sympathetic reaction experiments and one Large Scale Gap Test series to extract additional information of the response of the acceptor charges. The simulated arrival times were compared with the measured data at the fibreoptic array positions. Finally, the shock sensitivity curve that summarizes the critical combination of peak shock pressure P and the derived parameter P(2)t was described for the PBXN-109 formulations and compared with curves reported for other explosives.