The US Green Building Council's LEED for Existing Buildings (LEED-EB) rating system relies upon several standards and procedures developed by ASHRAE. Some are well known, such as the ASHRAE Standard 62.1-2007 Ventilation Rate Procedure, but need to be applied under different circumstances than they have typically been in the past. Others, such as ASHRAE Procedures for Commercial Building Energy Audits, were lesser known several years ago, before LEED-EB was introduced. Such terms as "ASHRAE Level I" and "ASHRAE Level II" Energy Audits have now been popularized in the building industry. This paper will address the LEED-EB requirements that rely on these ASHRAE tools and resources and discuss the challenges to the engineer regarding proper application under various existing building scenarios. It will explain the pertinent concepts and definitions as presented in the ASHRAE resource documents, and present strategies for how these ASHRAE resources can most effectively be utilized in the LEED-EB certification process.