Magnetic resonance imaging offers a means of observing the internal structure of the brain where traditional procedures of embedding, sectioning, staining, mounting, and microscopic examination of thousands of sections are not practical. Furthermore, internal structures can be analyzed in their precise quantitative spatial interrelationships, which is difficult to accomplish after the spatial distortions often accompanying histological processing. For these reasons, magnetic resonance imaging makes specimens that were traditionally difficult to analyze, more accessible. In the present study, images of the brain of a white whale (Beluga) Delphinapterus leucas were scanned in the coronal plane at 119 antero-posterior levels. From these scans, a computer-generated three-dimensional model was constructed using the programs VoxelView and VoxelMath (Vital Images, Inc.). This model, wherein details of internal and external morphology are represented in three-dimensional space, was then resectioned in orthogonal planes to produce corresponding series of "virtual" sections in the horizontal and sagittal planes. Sections in all three planes display the sizes and positions of such structures as the corpus callosum, internal capsule, cerebral peduncles, cerebral ventricles, certain thalamic nuclear groups, caudate nucleus, ventral striatum, pontine nuclei, cerebellar cortex and white matter, and all cerebral cortical sulci and gyri. Anat Key words: brain; neuroanatomy; cetacean; odontocete; white whale; Beluga; MRI Odontocetes (toothed whales, dolphins, and porpoises) have undergone a number of evolutionary modifications from their terrestrial ancestral state. Among these changes was a major increase in relative brain size. Several modern odontocete species possess encephalization levels second only to modern humans when brain-body allometry is taken into account (Ridgway and Brownson, 1984;Marino, 1998). An arguably equally dramatic transformation of odontocetes occurred in the anatomical structure and organization of their brains. Compared with many other mammalian brains, odontocete brain morphology is unusual in many respects. Researchers have stated that "…the lobular formations in the dolphin brain