The functions of the vomeronasal and olfactory systems are evaluated within the broad context of chemical communication in mammals. Five main points are stressed. First, there are a variety of types of chemical signals, ranging from classic pheromones to odor quality signals, all of which are important for communication. Second, the vomeronasal organ is primarily responsible for mediating responses to some, but by no means all, pheromone-like signals. Third, the olfactory system mediates responses to some pheromone-like signals. Fourth, the vomeronasal system mediates some responses to odor quality signals. Thus, not all receptors in the vomeronasal organ are involved in detection of pheromones. Fifth, the vomeronasal and olfactory systems often interact to mediate responses to odor signals. In sum, it is important to maintain a broad, balanced view and to avoid oversimplifications if we are to advance our understanding of the sensory mechanisms underlying responses to chemical signals and other odors.