The stellate ganglia of Macaca nemestrina were studied with the electron microscope, using the conventional and chromate-dichromate methods of aldehyde fixation. The principal neurons are multipolar and mostly mononucleated. They measure between 10 and 50 microns in their average somal diameters. The organelles of the perikaryon are arranged in perinuclear, intermediate and peripheral zones. Unusual organelles consisting of stacks of closely apposed paired membranes, with or without dense bodies studded on their surfaces, are encountered. Nuclear eccentricity is a regular feature of the neuron and the nuclear membrane shows a varying degree of invagination. All parts of the neurons are surrounded by satellite or Schwann cells though dendritic surfaces in direct contact with the basal lamina associated with the satellite cells are not uncommonly seen. Features peculiar to dendrites have been described. Structures resembling dendritic growth cones are present in abundance. Most synapses are axodendritic; axosomatic synapses are much less frequently encountered. While most synapses are of the simple type, complex types are also present. Desmosome-like junctional complexes exist between dendrites, dendrites and somata and axons and dendrites. Differences between Schwann cells of myelinated axons and those of myelinated axons and satellite cells have been noted. In addition to an abundance of macrophages, other connective tissue cells such as mast cells, fibroblasts and plasma cells are also present. Degenerative profiles observed include neuronal cell bodies and cell processes, especially dendrites. They are phagocytosed by the satellite cells and macrophages. The presence of degenerative profiles, chromatolytic neurons and structures resembling dendritic growth cones in the normal stellate ganglion has been discussed.