This pilot study will assess the prevalence of glucose intolerance (insulin resistance) in elderly individuals with normal fasting glucose levels. In addition, it will determine whether glucose intolerance among these non-demented elderly individuals is related to memory function, hippocampal size, and 24-hour urinary cortisol excretion. Fifty normal elderly subjects, 50 elderly subjects with minimal cognitive impairment (MCI), and 20 young individuals will be studied. The protocol will include neuropsychological measures, quantitative MRI of the hippocampus, baseline intravenous glucose tolerance testing (IV-GTT), and hydrocortisone- potentiated IV-GTT. Brain function will be evaluated by quantified EEG with power spectral analysis and by memory testing. Cortisol, insulin and ACTH will also be measured.