Recent findings suggest that coronary heart disease and stroke, and the associated conditions, hypertension and non-insulin dependent diabetes, originate through impaired growth and development during fetal life and infancy. These diseases may be consequences of 'programming', whereby a stimulus or insult at a critical, sensitive period of early life results in long-term changes in physiology or metabolism. Animal studies provide many examples of programming, which occurs because the systems and organs of the body mature during periods of rapid growth in fetal life and infancy. There are critical windows of time during which maturation must be achieved; and failure of maturation is largely irrecoverable.