The fine distribution of gamma-aminobutyric acid (GABA), aspartate and glutamate in the lateral and medial part of the human dentate nucleus was biochemically determined after microdissection of the grey and the white matter. The mean GABA concentrations of the lateral and medial grey matter were largely similar. The topographical distribution, however showed a higher concentration in the caudal part of the lateral grey than in other parts of dentate nucleus. In the medial section the GABA concentration was the lowest in the white matter. The surrounding white matter showed the highest GABA concentration on the caudal side of the lateral part of the dentate nucleus. Aspartate concentration was the highest in the lateral grey matter. On the ventral caudal side of the dentate nucleus the aspartate concentration was much higher compared to other parts of the surrounding white matter. Glutamate roughly showed a similar distribution pattern compared to aspartate, although no specific pattern in the surrounding white matter could be found. The results suggest specific entry and ending patterns for functionally verified afferent fibers to the dentate nucleus in man.