In three patients dementia without neurofibrillary tangles or Pick bodies antedated amyotrophy by several years. The motor neuron disorder in two patients was characterized by terminal bulbar symptoms; in one it was similar to classic amyotrophic lateral sclerosis. In two patients, quantitative studies of selected regions of the cortex using a computerized image analyzer disclosed, as in patients with senile dementia of Alzheimer type, a marked reduction in the number of neurons, especially those larger than 90 mu 2. The findings differed from those in Alzheimer dementia, however, in that the cells in the substantia innominata were not reduced and the levels of choline acetyltransferase and somatostatin-like immunoreactivity, determined in one patient, were within normal limits. A variable degree of sponginess of the upper layers of the cortex was attributed to attrition of pyramidal cell dendrites, observed in the one patient in whom Golgi study was successful. Because of severe degeneration of the substantia nigra in all three, the disease in these patients may represent a subset of motor neuron disease or a multisystem atrophy.