This report describes the approaches necessary for the measurement, monitoring and reporting of structure, biomass and carbon stocks in mangrove forests. Mangroves are coastal ecosystems providing numerous ecosystem services affecting both marine and terrestrial resources. In addition, they contain substantial carbon stocks and, due to high rates of deforestation, are significant sources of carbon emissions. Because of their value as carbon stocks and sinks and their numerous other benefits, mangroves could be excellent candidates for carbon mitigation programmes including Reducing Emissions from Deforestation and Forest Degradation, and Enhancing Forest Carbon Stocks in Developing Countries (REDD+). This publication outlines biologically relevant and statistically valid approaches to the efficient and accurate assessment of ecosystem structure, biomass and carbon stocks of mangrove forests.