The organization and relations between nerve, glial, chromaffin and other structural components of sympathetic ganglia of the cat were studied electron microscopically. Cholinergic, adrenergic and, probably, peptidergic terminals of axons making different contacts with the surrounding ganglionic cells and processes are shown with electron histochemical methods. Ultrastructural features of some dendrites are revealed which characterize them as sensory terminals of sympathetic ganglia. Besides the known axo-dendritic, axo-somatic and axo-axonal synapses, the ganglia show axo-glial synapses, and also dendro-dendritic and dendro-somatic contacts. It is established that preliminary destruction of ganglionic connections with the central nervous system is fatal only to a proportion of these interneuronal contacts while the rest of them persist. Synaptic complexes are found showing contacts of several axons and dendrites and representing a morphological substrate for convergence and divergence. No synapses are found whose presynaptic pole would be formed by a chromaffin cell. The functional role of these cells in the ganglia is discussed.