Environmental chemicals with hormone-like activity can disrupt the programming of endocrine signalling pathways that are established during perinatal life and result in adverse consequences that may not be apparent until much later in life. Increasing evidence implicates developmental exposure to environmental hormone mimics with a growing list of adverse health consequences in both males and females. Most recently, obesity has been proposed to be yet another adverse health effect of exposure to endocrine disrupting chemicals (EDCs) during critical stages of development. Obesity is quickly becoming a significant human health crisis because it is reaching epidemic proportions worldwide, and is associated with chronic illnesses such as diabetes and cardiovascular disease. In this review, we summarize the literature reporting an association of EDCs and the development of obesity, and further describe an animal model of exposure to diethylstilbestrol that has proven useful in studying mechanisms involved in abnormal programming of various oestrogen target tissues during differentiation. Together, these data suggest new targets (i.e. adipocyte differentiation and mechanisms involved in weight homeostasis) of abnormal programming by EDCs, and provide evidence that support the scientific term 'the developmental origins of adult disease'. The emerging idea of an association of EDCs and obesity expands the focus on obesity from intervention and treatment to include prevention and avoidance of these chemical modifiers.