Investigation of the metabolism of L-glutamic acid in slices of adult rat retina under aerobic conditions using the technique of quantitative automatic paper radio-chromatography is described. L-glutamic acid was converted into aspartate, $\gamma $-aminobutyrate, glutamine and carbon dioxide. In the presence of added glucose, the formation of glutamine and $\gamma $-aminobutyrate from glutamate was markedly increased, whereas the formation of glutamine was not appreciably affected by the addition of pyruvate to the medium. The addition of either glucose or pyruvate caused a marked decrease in the production of aspartate from glutamate. The production of carbon dioxide from glutamate, or from glutamate in the presence of glucose or pyruvate, appears to be quantitatively the same.