Insulin-dependent diabetes mellitus (IDDM) is one of the most important chronic diseases of children worldwide. IDDM leads to an 8- to 10-fold excess risk of mortality in developed countries, whereas in developing countries, most cases die within a few years. A 60-fold international gradient in IDDM incidence has been reported, and epidemic periods have been identified. A new World Health Organization program, Multinational Project for Childhood Diabetes (Diabetes Mondiale or DIAMOND), has been developed to investigate and characterize global incidence, mortality, and health care. Over 10 yr (1990-1999), this study will collect population-based data concerning IDDM in greater than 90 centers in 50 countries worldwide. The goals of DIAMOND are to collect standard information on incidence, risk factors, and mortality associated with IDDM; evaluate the efficiency and effectiveness of health care and the economics of diabetes; and establish national and international training programs in diabetes epidemiology. It is hoped that the DIAMOND project will be instrumental for the prevention of this serious disease and its sequelae.