The piriform cortex contains two main classes of principal neurons: semilunar cells (SLs) and pyramidal cells (PYRs). Both SLs and PYRs receive direct olfactory bulb input. However, while SLs only receive excitatory inputs from the olfactory bulb, PYRs also receive excitatory synaptic inputs from SLs and other PYRs, forming an extensive, long-range recurrent network within the piriform cortex. SLs only receive excitatory inputs from the olfactory bulb. By contrast, PYRs receive direct olfactory bulb input and excitatory synaptic inputs from SLs and other PYRs, forming an extensive, long-range recurrent network within the piriform cortex. What specific roles do SLs and PYRs play in odor processing and guiding odor-driven behaviors? Based on observations in brain slices, cortical odor processing has been proposed to occur in two sequential stages in which SLs first receive and integrate olfactory bulb input. PYRs then receive, transform, and transmit SL input. Is odor information sequentially processed in vivo? We have developed a mouse line that expresses Cre recombinase selectively in SLs in the piriform cortex, providing a genetic handle to identify and control the activity of SLs in vivo. We found that cortical odor processing in vivo occurs primarily through parallel channels of SLs and PYRs, with PYRs exhibiting little dependence on SL input. In preliminary investigations, we found that SLs decorrelate similar inputs while PYRs generalize according to the dominant odor component in mice performing an odor discrimination task. Moreover, SLs are required to form, but not to retrieve, learned odor associations. Together, these observations support a model in which SLs and PYRs may function analogously to the dentate gyrus and CA3 regions in the hippocampus.