BACKGROUND:Complications from unsafe abortion are believed to account for the largest proportion of hospital admissions for gynaecological services in developing countries. The WHO estimates that one in eight pregnancy-related deaths result from unsafe abortions. The social stigma and legal restrictions associated with abortion in many countries means that data on the magnitude of this problem are scarce; this article estimates the rate and numbers of hospital admissions resulting from unsafe abortions in developing countries to help quantify the problem. METHODS:National estimates of abortion-related hospital admissions in women aged 15-44 years were compiled for 13 developing countries: Africa (Egypt, Nigeria, and Uganda), Asia (Bangladesh, Pakistan, and the Philippines), and Latin America and the Caribbean (Brazil, Chile, Colombia, Dominican Republic, Guatemala, Mexico, and Peru). These data were combined with supplementary data from five countries in sub-Saharan Africa (Burkina Faso, Ghana, Kenya, Nigeria, and South Africa) to give estimates for the three world regions. FINDINGS:The annual hospitalisation rate varies from a low of about 3 per 1000 women in Bangladesh to a high of about 15 per 1000 in Egypt and Uganda. Nigeria, Pakistan, and the Philippines have rates of 4-7 per 1000, and two countries in Latin America with recent data have rates of almost 9 per 1000. In the developing world as a whole, an estimated five million women are admitted to hospital for treatment of complications from induced abortions each year. This equates to an average rate of 5.7 per 1000 women per year in all developing regions, excluding China. By comparison, in developed countries complications from abortion procedures or hospitalisation are rare. INTERPRETATION:These results help quantify the magnitude of the adverse health effects of unsafe abortion in developing countries and highlight the need for improved access to post-abortion care. The provision of abortion services is changing to include the drug misoprostol and this could reduce the severity of abortion complications and the number of women who are hospitalised. Researchers will need to monitor these changes to provide countries with up-to-date information on illness and death from unsafe abortion. Improved contraceptive services are necessary to prevent unintended pregnancy. However, increasing access to safe abortion services is the most effective way of preventing the burden of unsafe abortion, and remains a high priority for developing countries.