This document provides guidance on migrating from OHSAS 18001 to the new ISO 45001 standard for occupational health and safety management systems. There are new requirements in ISO 45001, including greater emphasis on leadership commitment, worker participation, understanding organizational context, and risk-based thinking. Organizations certified to OHSAS 18001 will need to update their systems to meet the new ISO 45001 requirements within three years of its publication in March 2018. This guide reviews the key changes between the standards and provides advice to help organizations interpret requirements and manage the transition process.