The tumor protein p73 is involved in a variety of functions including neural development. p73-KO mice lack exploratory genital and mating behavior and are sterile. Since p73 is highly expressed in the vomeronasal organ (VNO), we examined centers related to the pheromonal pathway from embryonic day (E) 12 to adulthood, by using immunohistochemistry. In the p73 KO mouse, the VNO is smaller compared to the WT from the onset of development. However, the vomeronasal nerve (VNN) is present though reduced in size, and serves as a migration substrate for GnRH+ neurons from the olfactory placode to the forebrain. In later stages, the VNN does not reach the accessory olfactory bulb (AOB), and the glomerular layer of the AOB does not form, therefore, there is no synaptic connection between the VNN and the AOB, leading to a disruption of the pheromonal pathway. The adult AOB is hypoplastic with very few mitral cells, few external granular cells but many interneurons in the internal granular layer. The main olfactory bulb is also severely reduced in size, and the glomerular layer is smaller and less well defined. In addition, the medial nucleus of the amygdala is strongly reduced in size.GnRH+ neurons are present in hypothalamus and septum, but their number is significantly lower than in WT.The presence of p73 is thus required for sexual behavior and reproduction at the level of the CNS.