Brain biopsy was performed on a 61-year-old woman with a four-year history of progressive dementia. Light microscopy revealed typical amphophilic, argentophilic Pick bodies in cortical neurons, many of which were ballooned and displayed central chromatolysis. A few senile plaques were apparent in the neuropil, but neurofibrillary tangles were not found. The Pick bodies were seen by electron microscopy to be made up of 100 Angstrom filaments, ribosomes, vesicles, lipochrome, and some 240 A tubules. Inclusions were not sharply demarcated from the remainder of the cytoplasm and closely resembled the central chromatolysis of axonal reaction. Therefore, it is proposed that Pick cells are the result of retrograde or transsynaptic degeneration and that the neuron aggregates whatever fibrillar material it has and can make. The plaques were quite typical except that they lacked twisted tubules. (26:97-108, 1972)