Diabetes mellitus is one of the main threats to human health in the 21st century. The prevalence of diabetes ranges from nearly 0 per cent in New Guinea to 50 per cent in the Pima Indians. The past two decades have seen an explosive increase in the number of people diagnosed with diabetes world-wide. The World Health Organization (WHO) estimated that there were 135 million diabetics in 1995 and this number would increase to 300 million by the year 2025. India leads the world today with the largest number of diabetics in any given country. In the 1970s, the prevalence of diabetes among urban Indians was reported to be 2.1 per cent and this has now risen to 12.1 per cent. Moreover, there is an equally large pool of individuals with impaired glucose tolerance (IGT), many of whom will develop type 2 diabetes mellitus in the future. Diabetes can affect nearly every organ system in the body. The Chennai Urban Population Study (CUPS) showed that prevalence of diabetic retinopathy, nephropathy and neuropathy is not very different in urban south Indians compared to that reported among Europeans. However, coronary artery disease (CAD) occurs with increased prevalence and at a younger age (premature CAD), while peripheral vascular disease showed the opposite trend, with lower prevalence compared to that reported in Europeans. There is an urgent need for lifestyle intervention, with the incorporation of a healthy diet, an increase in physical activity and weight reduction as a means of preventing diabetes in those who are in the prediabetic stage and thus prevent the diabetes epidemic, which is looming large in our country.