Vulnerable neuronal populations in Alzheimer disease display a phenotype that is characteristic, in many ways, of cancer cells. This includes the ectopic expression of a hoard of proliferative cell cycle markers and aberrant activation of mitogenic and oncogenic signaling pathways. These findings have led us to hypothesize that neurodegeneration in Alzheimer disease, like cancer, is a disease of inappropriate cell cycle control. In this review, after a brief summary of cell cycle control, we discuss oncogenic and cell cycle alterations in Alzheimer disease and critically assess their relationship to other facets of disease pathogenesis. © RPA Publications. All rights reserved.