AMPA receptors (AMPARs), a subtype of glutamate receptor, contribute to olfactory processing in the olfactory bulb (OB). These ion channels are comprised of various combinations of the subunits GluR1-4, which bestow certain properties. For example, AMPARs that lack GluR2 are highly permeable to Ca⁺⁺ and generate inwardly rectifying currents. As increased intracellular Ca⁺⁺ could trigger a host of Ca⁺⁺ -dependent odor-encoding processes, we used whole-cell recording, histologic, and immunocytochemical (ICC) techniques to investigate whether AMPARs on rat OB neurons flux Ca⁺⁺. Application of 1-naphthylacetyl spermine (NAS), a selective antagonist of calcium-permeable AMPARs (CP-AMPARs), inhibited AMPAR-mediated currents in subsets of interneurons and principle cells in cultures and slices. Addition of spermine to the electrode yielded inwardly rectifying current-voltage plots in some cells. In OB slices, olfactory nerve stimulation elicited excitatory responses in juxtaglomerular and mitral cells. Bath application of NAS + AP5 (to isolate AMPARs) suppressed the amplitudes of these synaptic responses compared with responses obtained in AP5 alone. Cobalt staining, which involves the kainate-stimulated influx of cobalt through CP-AMPARs, produced diverse patterns of labeling in cultures and slices, as did ICC with a GluR2-selective antibody. These results suggest that subsets of OB neurons express of calcium-permeable AMPARs, including functional CP-AMPARs at synapses. Calcium entry into cells via these receptors could influence odor encoding by modulating K⁺ channels, NMDA receptors, and calcium-binding proteins, or facilitating synaptic vesicle fusion.