This document describes activities of the secretariat relating to greenhouse gas (GHG) inventory review during the period January 2003 to March 2004 and activities planned for the remainder of 2004. It covers work undertaken by the secretariat to improve the effectiveness, efficiency and consistency of the review process, in accordance with the review guidelines, and thus to help ensure the reliability of information on GHG emissions and trends provided to the Conference of the Parties and its subsidiary bodies.