During the ultrastructural investigation of the cat's subthalamic nucleus (STN), profiles exhibiting features attributed to dendrites and simultaneously containing synaptic vesicles, were encountered. Most of them take part in synaptic triads, usually as an intermediate component. On the basis of their electron microscopical appearance, and synaptic relationships, they might be discriminated, as a distinct ultrastructural entity. Although not conspicuous in number, they might have their own contribution to the synaptic events taking place in the STN.