The literature on cognitive function and Alzheimer's disease in non-insulin-dependent diabetes, impaired glucose tolerance and hyperinsulinaemia are briefly summarized. Neuropsychological, epidemilogical and endocrine contributions are reviewed, with an emphasis on the insulin hypothesis as a potential pathophysiological mechanism for Alzheimer's disease. Curr Opin Neurol 11:673-677. (C) 1998 Lippincott Williams & Wilkins.