It has been suggested that increased activity of the hypothalamic-pituitary-adrenal axis may link low birth weight with subsequent development of cardiovascular risk factors and disease. Two hundred and five men, aged 66–77 yr, who were born and still live in East Hertfordshire underwent an overnight very low dose (0.25 mg) dexamethasone suppression test followed by a low dose 1-μg ACTH-(1–24) stimulation test. A 24-h urine sample was collected for analysis of cortisol metabolites by gas chromatography/electron impact mass spectrometry. Men with lower birth weight had enhanced responses of plasma cortisol to ACTH-(1–24) (P = 0.03), increased total urinary cortisol metabolite excretion (after adjustment for confounding effects of increased obesity and lean body mass in high birth weight men; P = 0.04), but no difference in plasma cortisol after dexamethasone. Features of the metabolic syndrome were independently associated with enhanced adrenal responsiveness to ACTH-(1–24) (raised blood pressure, P = 0.02; glucose intolerance, P = 0.09; hypertriglyceridemia, P = 0.02), with trends to increased urinary cortisol metabolite excretion, but not with differences in plasma cortisol after dexamethasone. Men with low birth weight and/or the metabolic syndrome have increased activity of the hypothalamic-pituitary-adrenal axis. This may be an important mechanism underpinning the effects of events in early life on later cardiovascular disease.