There is now overwhelming evidence that much of our predisposition to adult illness is determined by the time of birth. These diseases appear to result from interactions between our genes, our intrauterine environment and our postnatal lifestyle. Those at greatest risk are individuals in communities making a rapid transition from lives of 'thrift' to a lives of 'plenty'. From a global perspective, such origins of diabetes, coronary heart disease and stroke, should render research in these fields as one of the highest priorities in human health care. Prevention will be enhanced by elucidation of the mechanisms by which the fetus is programmed by the mother for the life she expects it to live. At the present time, there is evidence that fetal nutrition and premature exposure to cortisol are effective intrauterine triggers, but a multitude of alternative pathways require investigation. It is also likely that programming extends across generations, and may involve the embryo and perhaps the oocyte. An oocyte that becomes an adult human develops in the uterus of its grandmother, so further research is required to describe the role of environments of grandmothers and mothers in predisposing offspring to health or illness in adult life.