Objective— To assemble standardized estimates of abnormal glucose tolerance in adults in diverse communities worldwide and provide guidelines for the derivation of comparable estimates in future epidemiological studies. Research Design and Methods— The project was limited to population-based investigations that had used current WHO criteria for diagnosis and classification of abnormal glucose tolerance. Raw data were obtained by WHO from surveys conducted during 1976–1991 of over 150,000 persons from 75 communities in 32 countries. Data within the truncated age range of 30–64 yr were adjusted to the standard world population of Segi. Age-specific prevalences also are reported for selected populations. Results— Within the chosen age range, diabetes was absent or rare (<3%) in some traditional communities in developing countries. In European populations, age-standardized prevalence varied from 3 to 10%. Some Arab, migrant Asian Indian, Chinese, and Hispanic American populations were at higher risk with prevalences of 14–20%. The highest prevalences were found in the Nauruans (41%) and the Pima/Papago Indians (50%). Age-standardized prevalence of IGT was low (50% were previously undiagnosed. In both Chinese and Indian migrant populations, relative prevalence was high when compared with indigenous communities. Conclusions— Diabetes in adults is now a global health problem, and populations of developing countries, minority groups, and disadvantaged communities in industrialized countries now face the greatest risk.