Recent studies have established the presence of an olfactory input to the mediodorsal nuclear complex of the thalamus, an area which has been known primarily as the thalamic dependency of orbitofrontal cortex. This new evidence for an olfactory thalamocortical relay brings olfaction into line with other sensory systems and provides fresh information on the largely unknown functions of MD and orbitofrontal cortex. The objective of the proposed research is a combined electrophysiological and autoradiographic delimitation of the thalamic and cortical olfactory projection fields and a determination of their associations with two other apparently related projection fields: amygdalar and gustatory. This work should serve as a necessary prelude to functional electrophysiological studies.