This document reports the global, regional, and country estimates of maternal mortality in 2005, and the findings of the separate assessments of trends of maternal mortality levels since 1990. It summarizes the challenges involved in measuring maternal mortality and the main approaches to measurement, and explains the development of the 2005 maternal mortality estimates and the interpretation of the results. The final section discusses the use and limitations of the estimates, with an emphasis on the importance of improved data quality for maternal mortality estimation. The appendices present data tables of country estimates according to data source and different regional groupings for WHO, UNICEF, UNFPA and The World Bank.