Previous research has indicated that volatile odorants are detected through the main olfactory epithelium (MOE), whereas pheromones are detected via the vomeronasal organ (VNO). Gene disruption studies have established that olfactory signaling through the MOE is mediated through receptor stimulation of type 3 adenylyl cyclase (AC3). Mice lacking AC3 cannot detect odorants through the MOE. Recently, it was discovered using olfactory-based behavioral assays that AC3 mutant mice can detect some volatile odorants. An analysis of these mutant mice led to the surprising discovery that some odorants are detected through the VNO.