This SAE Aerospace Information Report (AIR) covers the generation of used phosphate ester aviation hydraulic fluid (AS1241) that is deemed waste because it does not meet in-service limits for use in aircraft. This document also lists the relevant United States Environmental Protection Agency (U.S. EPA) regulations on used hydraulic fluid that are in force at the time of this report's publication. Regulations of other countries as well as those for states and municipalities should be consulted prior to initiating any of the waste disposal recommendations listed here.