The brain neuronal network is complex. This elaborated wiring relies on an extensive number of guidance cues and receptors. Based on studies from several neuronal systems, numerous molecules have been characterized in the navigation of neurites. Here, we studied the wiring of mouse olfactory sensory neurons towards an anterior brain structure, the olfactory bulb. Each olfactory sensory neuron population usually forms one glomerulus on the lateral side and one on the medial side of each bulb in a symmetric fashion, creating thus intra-bulb mirror images. Recent studies suggested a role for Neuropilin 1 and Semaphorin 3a in axonal targeting along the antero-posterior axis of the olfactory bulbs. We studied the role played by these molecules in the glomerular map formation. We used genetically controlled removal of either Neuropilin 1 or Semaphorin 3a to assess this role.