Reliable information on causes of death is essential to the development of national and international health policies for prevention and control of disease and injury. Medically certified information is available for less than 30% of the estimated 50.5 million deaths that occur each year worldwide. However, other data sources can be used to develop cause-of-death estimates for populations. To be useful, estimates must be internally consistent, plausible, and reflect epidemiological characteristics suggested by community-level data. The Global Burden of Disease Study (GBD) used various data sources and made corrections for miscoding of important diseases (eg, ischaemic heart disease) to estimate worldwide and regional cause-of-death.patterns in 1990 for 14 age-sex groups in eight regions, for 107 causes. Preliminary estimates were developed with available vital-registration data, sample-registration data for India and China, and small-scale population-study data sources. Registration data were corrected for miscoding, and Lorenz-curve analysis was used to estimate cause-of-death patterns in areas without registration. Preliminary estimates were modified to reflect the epidemiology of selected diseases and injuries. Final estimates were checked to ensure that numbers of deaths in specific age-sex groups did not exceed estimates suggested by independent demographic methods. 98% of all deaths in children younger than 15 years are in the developing world. 83% and 59% of deaths at 15-59 and 70 years, respectively, are in the developing world. The probability of death between birth and 15 years ranges from 22.0% in sub-Saharan Africa to 1.1% in the established market economies. Probabilities of death between 15 and 60 years range from 7.2% for women in established market economies to 39.1% for men in sub-Saharan Africa. The probability of a man or woman dying from a non-communicable disease is higher in sub-Saharan Africa and other developing regions than in established market economies. Worldwide in 1990, communicable, maternal, perinatal, and nutritional disorders accounted for 17.2 million deaths, non-communicable diseases for 28.1 million deaths and injuries for 5.1 million deaths. The leading causes of death in 1990 were ischaemic heart disease (6.3 million deaths), cerebrovascular accidents (4.4 million deaths), lower respiratory infections (4.3 million), diarrhoeal diseases (2.9 million), perinatal disorders (2.4 million), chronic obstructive pulmonary disease (2.2 million), tuberculosis (2.0 million), measles (1.1 million), road-traffic accidents (1.0 million), and lung cancer (0.9 million). Five of the ten leading killers are communicable, perinatal, and nutritional disorders largely affecting children. Non-communicable diseases are, however, already major public health challenges in all regions. Injuries, which account for 10% of global mortality, are often ignored as a major cause of death and may require innovative strategies to reduce their toll. The estimates by cause have wide Cls, but provide a foundation for a more informed debate on public-health priorities.