In quantitative neuroanatomy and neuropathology, large neuronal systems are frequently analyzed on the basis of small tissue blocks, assuming that volume changes of the various compartments of the tissue block can be corrected by an overall factor. Blocks of cerebral cortex and white matter of the frontal lobe, thalamus and striatum (228) were prepared from 13 human brains and embedded in paraffin. The mean shrinkage in the paraffin sections was 51% for the cerebral cortex and 42% for the white matter. An overall correction factor for tissue blocks both with cerebral cortex and white matter results in an underestimation of cerebral cortex and an overestimation of white matter.