• We present a correlation of the morphometric cell density analysis with previous biochemical findings for the inferior olivary nucleus and Purkinje cell layer of the cerebellum from 10 patients (three kindreds) with dominant olivopontocerebellar atrophy. We have analyzed brain amino compounds of these patients and found a decrease of aspartic acid and glutamic acid in the cerebellar cortex and of aspartic acid in the inferior olives. The cell density analysis revealed decreased cell counts, with a mean of 34% of olivary cells and 42% of Purkinje cells surviving when compared with 10 control brains. The cell counts were then correlated with the amino acid analyses. The correlation co-efficient for aspartic acid content and surviving neurons in the inferior olive was.87 and that for aspartic acid content and Purkinje cell density was.86. Comparison of glutamic acid content and Purkinje cell density yielded a correlation coefficient of.75. The correlations appear to indicate a relationship between these particular cells or the area they occupy and the decreased content of the two amino acids.