The localization of acetylcholinesterase (AChE) activity in the nuclei of the amygdaloid body of man was studied by Gerebtzoff's modification of Koelle's acetylthiocholine method on 10 human brains. To compare the histochemical results with the cytoarchitectionics, additionally sections from 10 human brains were stained with cresyl violet. The intensity of AChE activity in the different amygdaloid nuclei varied widely. The high AChE activity occurred in the basal lateral nucleus and in the lateral part of the central nucleus. Very little activity was found in the medial nucleus and in the intermediate part of the central nucleus. All remaining nuclei showed AChE activity of moderate intensity. In almost each amygdaloid nucleus, differences of AChE activity among various areas were observed. In the amygdala of man all nuclei described in animals were found except nucleus of the lateral olfactory tract. Most of the human amygdaloid nuclei show more differentiated structure than in lower mammals in terms of not only cytoarchitectonic subdivision, but also in the intensity of AChE activity.