The metabolic and cardiovascular complications associated with in-utero undernutrition have been identified during the past 10 years. Reduced fetal growth is independently associated with an increased risk for the development of cardiovascular diseases, the insulin resistance syndrome and its components: hypertension, dyslipidemia, impaired glucose tolerance, and type 2 diabetes. All appear to result from the initial development of insulin resistance that seems to be a key component underlying this association. Several hypotheses have been proposed over the past 10 years to understand this unexpected association. Each of them points to either a detrimental fetal environment or genetic susceptibilities or interactions between these two components as playing a critical role in this context. The hypothesis that this association could be the consequence of genetic/environmental interactions remains at the moment the most attractive. Although the mechanism remains unclear, there is also some evidence that adipose tissue plays a role in the emergence of insulin resistance associated with in-utero undernutrition.