Abstract Cortical cells have been counted in 11 areas of brain from each of 64 normal subjects from 18 to 95 years of age, all cases studied being selected after careful consideration of their clinical records and detailed histological examination of the brain. Cells (features) in cresyl fast violet stained 20 μm paraffin sections were initially divided into 8 groups according to size in multiple columns of cortical tissue; statistical evaluation of the results showed that there were 3 populations of cortical cells, based on size discrimination, which behaved in significantly different ways. The smallest cells have been designated “glial cells” and the other two groups “small” and “large” neurons. The number of cells in all three groups decreased from youth to old age, the least loss being in the “glial cells” and the greatest (up to 60%) in “large neurons”. The variation and statistical significance of cell loss in each cell group in the different areas examined is described, and the findings in this investigation discussed in relation to previous studies using manual methods.