The Hazard Communication standard (HCS) has been revised to align with the United Nations Globally Harmonized System of Classification and Labelling of Chemicals (GHS Revision 3, 2009). This includes updates to the requirements for labeling and for safety data sheets (SDSs). This instruction outlines the revisions to the HCS, such as the revised hazard classification of chemicals, standardizing label elements for containers of hazardous chemicals, and specifying the format and required content for safety data sheets. It explains how the revised standard is to be enforced during its transition period and after the standard is fully implemented on June 1, 2016.