The intensity of research on the central catecholaminergic neuron systems has continued unabated since last year's review of the dopaminergic systems (Moore & Bloom 1978). Although our original intent was to attempt a review of the structure and function of all these systems within one chapter, the richness of important details deserving of inclusion resulted in a contri bution exceeding the pages available. As a result, we have had an additional year in which to acquire even more material pertaining to the central adrenergic and noradrenergic neuron systems. It is the noradrenergic sys tems in particular that present the more flagrant violations (Dismukes 1977) of the structural and functional archetypes normally attributed to central neuronal systems. Their widespread efferent trajectories with high degrees of collateral arborization, their marked propensity for the expression of post-lesion regrowth, and their unique combination of functional actions, enriched in some cases by association with adenylate cyclase, all combine