The prevalence of obesity and diabetes has risen dramatically in the United States and in other regions of the world over the past two decades. Perhaps even more important is that these metabolic diseases are rising dramatically in our children. There is considerable evidence that the risk factors for obesity and diabetes may begin early in life, during pregnancy, and in early childhood. Evidence shows that rapid weight gain in the first few months of life is associated with obesity later in life. Obesity and diabetes, like other complex diseases, are caused by a series of interactions between genetic, behavioral, and environmental factors. While there are certainly important genetic and lifestyle components contributing to obesity and diabetes, evidence also points to a contributing role of environmental influences, particularly exposure to endocrine disrupting chemicals during periods of development. Here we review current epidemiological and experimental relationships between these chemicals, their mechanisms of action, and the role of environmental exposures in the obesity and diabetes epidemic.