We here report odor-induced mapping patterns of c-fos-like protein (Fos) immunoreactivity in the rat olfactory bulb under urethane anesthesia. Regional patterns of cells with nuclei expressing Fos, plotted on a spread-out reconstruction of the mitral cell layer, were strikingly comparable to data from the 2-deoxyglucose method, by which different foci of the most-labelled glomeruli of metabolic activity were demonstrated using different odors. Cells in the glomerular, external plexiform, and granule cell layers were also labelled.