The white sucker, Catostomus commersoni, is among the many fishes classified as minnows (order Cypriniformes). Minnows are a morphologically diverse teleost (bony fish) group whose brains have been examined previously in both a morphological and experimental context. Two species of minnows, goldfish (Carasius auratus) and European carp (Cyprinus carpio) have been commonly used as model systems for experimental neuroanatomical studies.The purpose of this present study is to catalog the brain of the white sucker for its use in future studies and as a comparative reference for the study of other catostomids. In particular, the neuronal connections of the cranial nerves could be explored once the brain has been characterized. This species was chosen because of its position as the outgroup for all other members of the genus Catostomus, and the fact that it is relatively easy to obtain. This study focuses on two areas: descriptions of the gross morphology of the brain of the white sucker, and histological characterizations of the nuclei of the brain of the white sucker. / Department of Physiology and Health Science