Over the past decade there has been an increasing concern about the impact of chronic, noncommunicable diseases on the health of developing world populations. Traditionally, major causes of illness and death in developing countries have been linked to infectious diseases and undernutrition, and these are still major public health problems in several regions of the world. But recent projections indicate that in 20 y noncommunicable diseases will account for over 60% of the disease burden and mortality in the developing world. Obesity is recognized as an underlying risk factor for many of these chronic conditions. As in developed societies, the risk for obesity in developing countries is also strongly influenced by diet and lifestyle, which are changing dramatically as a result of the economic and nutrition transition. This symposium discusses key aspects of the phenomenon of obesity in the developing world and provides some specific examples from countries facing increasing prevalence of that condition.