The growing prevalence of obesity and associated diseases such as type II diabetes is a major health concern, including among children. Epidemiological and animal studies suggest that alteration of the metabolic and hormonal environment during critical periods of development is associated with increased risks for obesity and type 2 diabetes in later life. There is general recognition that the developing brain is more susceptible to environmental insults than the adult brain. In particular, there is growing appreciation that developmental programming of neuroendocrine systems by the perinatal environment represents a possible cause for these diseases. This talk will summarize the major stages of hypothalamic development and will discuss potential periods of vulnerability for the development of hypothalamic circuits regulating feeding and glucose regulation. It will also provide an overview of recent evidence concerning the action of perinatal hormones (including leptin and ghrelin) and semaphorins in programming the development and organization of hypothalamic circuits that regulate feeding and glucose homeostasis.