Elderly patients with depression and Alzheimer-type dementia (ATD) were compared with age-matched control subjects using a protocol which measured Cortisol, adrenocorticotrophic hormone (ACTH) and N-terminal pro-opiomelanocortin (N-POMC) to determine diurnal variation and the effect of dexamethasone administration. Depressed patients had significantly elevated Cortisol concentrations both before and after dexamethasone administration. Basal ACTH and N-POMC concentrations were normal in depressed patients but were both elevated, compared with controls, after dexamethasone. By contrast, in ATD patients, Cortisol was elevated only after dexamethasone, as was ACTH, but not N-POMC. This may imply that the pattern of secretion of POMC-derived peptides underlying increased Cortisol secretion is different in ATD from that in depression.