The objective of this study was to ascertain the impact of aging and Alzheimer disease (AD) on brain cholesterol (CH), CH precursors and oxysterol homeostasis. Altered CH metabolism and up-regulation of heme oxygenase-1 (HO-1) are characteristic of AD-affected neural tissues. We recently determined that HO-1 over-expression suppresses total CH levels by augmenting liver X receptor-mediated CH efflux and enhances oxysterol formation in cultured astroglia. Lipids and proteins were extracted from post-mortem human frontal cortex derived from subjects with sporadic AD, mild cognitive impairment (MCI) and no cognitive impairment (NCI; n=17 per group) enrolled in the Religious Orders Study, an ongoing clinical-pathologic study of aging and AD. ELISA was used to quantify human HO-1 protein expression from brain tissue and GC-MS to quantify total CH, CH precursors and relevant oxysterols. The relationships of sterol/oxysterol levels to HO-1 protein expression and clinical/demographic variables were determined by multivariable regression and non-parametric statistical analyses. Decreased CH, increased oxysterol and increased CH precursors concentrations in the cortex correlated significantly with HO-1 levels in MCI and AD, but not NCI. Specific oxysterols correlated with disease state, increasing neuropathological burden, neuropsychological impairment and age. A model featuring compensated and de-compensated states of altered sterol homeostasis in MCI and AD are presented based on the current data set and our earlier in vitro work.