Magnetic resonance imaging techniques have been developed to enable imaging of the live rat brain with thin (1.2-mm) slices and microscopic pixels (115 X 115 microns). Signal-to-noise ratios high enough to realize the microscopic resolution are obtained with rf coils designed for the subject and through the use of three-dimensional Fourier spin warp imaging. The technique yields 16 contiguous slices. Correlation with fixed pathologic specimens enables unequivocal identification of gray and white matter structures in the brain of a live 200-g rat. Structures clearly visible in the MR images include Ammon's horn, the hypothalamus, corpus callosum and substantia nigra, as well as a number of brainstem nuclei.