One-hundred thirty-four albino rats implanted with a single bipolar electrode aimed at a brainstem site were tested for self-stimulation. Six of these Ss were then subjected to small lesions at the stimulation site so that degeneration from reward and neutral regions could be compared. Structures not typically related to reward (substantia nigra, brachium conjunetivmn, ventral tegmental decussation, rubrospinal tract) yielded self-stimulation, while brainstem structures typically associated or implicated in the reward process (reticular formation, tegmental reticular nucleus, dorsal tegmental nucleus) did not yield self-stimulation behavior. Degeneration experiments supported the mapping work by implication of the brachium conjunctivum . as one reward pathway. The present results pointed to the significance of the extrapyramidal system in brainstem reward, and the possibility that the red nucleus may occupy a nodal position in this reward system.In spite of speculations relating the selfstimulation phenomenon to reticular formation function (Glickman & Schiff, 1967; Sharpless, 1958) or differentiating the former from the latter (Routtenberg, 1968b), the evidence so far available (Glickman, 1960;O'Donohue & Hagamen, 1967;Olds & Peretz, 1960) makes it difficult to specify what the precise nature of the relationship might be. As a first assessment of the problem, a comparison of self-stimulation points throughout the brainstem seemed necessary. As this study progressed it was also necessary to incorporate the Nauta (1957) technique to gain further information. In Experiment 1, therefore, are presented brainstem mapping data and in Experiment 2 are presented observations of axonal degeneration caused by lesions made at the site of self-stimulation.