We have examined chromatin in lymphocytes from patients with Alzheimer’s disease (AD) and from normal individuals of a range of ages. We have found that the neucleosome repeat length does not vary with age for normal individuals over the range 24–78 years and that there is no difference between the value for AD cells (mean and standard deviation, 202 ± 7 base pairs, bp) and for normals (207 ± 5 bp). The rate of digestion of chromatin in lymphocyte nuclei by micrococcal nuclease does not appear to differ significantly between old and young normals and AD pat