This paper reviews existing emission factors and activity data used in the energy sector (Part One) and the land-use change and forestry sector (Part Two) based on the available literature, including the initial national communications submitted by non-Annex I Parties and various GHG inventory reports. It describes the methodology used, assesses the reliability and accuracy of the collected data and highlights the major problems encountered by non-Annex I Parties during the preparation of the GHG inventories in these two sectors. Based on the analysis, a number of conclusions are drawn and recommendations made on how to improve the reliability and comparability of emission factors and activity data, with a view to enhancing the quality of national GHG inventories. The complete bibliographical references of the reviewed documents are listed at the end of the paper