Premature centromere division (PCD) represents a loss of control over the sequential separation and segregation of chromosome centromeres. Although first described in aging women, PCD on the X chromosome (PCD,X) is markedly elevated in peripheral blood lymphocytes of individuals suffering from Alzheimer disease (AD). The present study evaluated PCD,X, using a fluorescentin situhybridization method, in interphase nuclei of frontal cerebral cortex neurons from sporadic AD patients and age‐matched controls. The average frequency of PCD,X in AD patients (8.60 ± 1.20%) was almost three times higher (p < 0.01) than in the control group (2.96 ± 1.20). However, consistent with previous studies, no mitotic cells were found in neurons in either AD or control brain, suggesting an intrinsic inability of post‐mitotic neurons to divide. In view of the fact that it has been well‐documented that neurons in AD can re‐enter into the cell division cycle, the findings presented here of increased PCD advance the hypothesis that deregulation of the cell cycle may contribute to neuronal degeneration and subsequent cognitive deficits in AD.