The prevalence of type 2 diabetes is rising rapidly in all non-industrialised populations. By 2025, three-quarters of the world's 300 million adults with diabetes will be in non-industrialised countries, and almost a third in India and China alone. There is strong evidence that this epidemic has been triggered by social and economic development and urbanisation, which are associated with general improvements in nutrition and longevity, but also with obesity, reduced physical exercise and other diabetogenic factors. There is evidence too that fetal growth retardation and growth failure in infancy, both still widespread in non-industrialised populations, increase susceptibility to diabetes. An additional factor may be intergenerational effects of gestational diabetes occurring in mothers who grew poorly in early life and become obese as adults. Prevention of type 2 diabetes will require measures to promote exercise and reduce obesity in adults and children, alongside programmes to achieve healthy fetal and infant growth