One hundred adult humans were examined specifically for the presence of the opening of the vomeronasal organ (VNO) on the antero-inferior part of the nasal septum. This was found in 39% of patients. Twenty-seven human septums were removed at post mortem, examined macroscopically, sectioned coronally and examined microscopically. In 70% of these specimens, vomeronasal structures were identified. Histological examination failed to reveal any evidence that these organs may be functional. The human embryology and comparative anatomy of the VNO are reviewed. The physiological function in different vertebrates is also considered, and the significance of the findings in this study is assessed in the light of this evidence.