The sense of smell plays an essential role is communication in mammals. Individual recognition call be achieved an the sale basis of olfactory signals. The setting of the different stages in sexual behaviour involves smells coming from the male as well as the female, Sexual odours also interfere in the regulation of physiological processes. The different phases in the relationship between mother and young involves a critical Pole for olfactory communication. In every case studied the sense of smell acts by interacting with the other senses, in a way that is cumulative and often redundant.