IEC/TS 61000-5-9:2009(E) is to present a methodology to assess the impact of High-altitude Electromagnetic Pulse (HEMP) and High Power Electromagnetic (HPEM) environments on electronic systems. In this context a system refers to a collection of sub-systems, equipment and components brought together to perform a function. The techniques associated with this methodology and their advantages and disadvantages will be presented along with examples of how the techniques can be applied to evaluate the susceptibility of electronic systems such as those found in installations. This work is closely related to the evaluation of EMC system level susceptibility. The purpose of IEC/TS 61000-5-9:2009 is to provide information on available methods for the assessment of system-level susceptibility as a result of HEMP and HPEM environments. The advantages and disadvantages of the methods will be discussed along with examples of how the techniques should be employed. Typical systems have external connections, wired or wireless, and the assessment of these are included within this specification. IEC/TS 61000-5-9:2009 gives general guidance. It does not cover safety issues nor does it conflict with ITU-T efforts concerning the protection of telecommunications equipment. IEC/TS 61000-5-9:2009 has the status of a basic EMC publication in accordance with IEC Guide 107.