The distribution of denegerating axons following heat lesions in different parts of the olfactory cortex in the rat was studied with light- and electron-microscopic techniques. The almost complete absence of degenerating boutons in the lateral hypothalamus contrasts sharply with the abundance of terminal degeneration in extrahypothalamic regions such as the mediodorsal nucleus of the thalamus (MD), the anterior continuation of hippocampus, the olfactory tubercle and the fundus striati. The only part of the lateral hypothalamus that seems to receive a sizeable amount of fibers direct from olfactory cortex is the nuclei gemini. The olfactory projections of the thalamus seem to be related primarily to the medial subdivision of the MD. Although a significant number of fibers in the olfactory projection system join the stria medullaris in the anterolateral hypothalamus, they leave the stria at the level of the habenular complex to terminate in MD instead of the lateral habenular nucleus.