The aim of this review is to show how olfaction is a sensory modality of singular importance for the fine adjustment of early mother-infant interactions. While the precise role of maternal olfaction varies from one species to another, olfactory cues are in fact used in various aspects of parental care. Not only do infantile odors become very potent stimuli allowing the normal development of maternal care but they also provide a basis for individual recognition of the offspring in some species. Recognizable olfactory signatures reflected the product of individual's genotype and are also influenced by the environment. Highly specialized neural mechanisms for processing of the infant signals have been developed. While there is no functional specificity of either the main or the accessory olfactory systems in the onset of maternal behavior among species, only the main olfactory system is implicated when individual odor discrimination of the young is required. Neural Structures, such as the main olfactory bulb, undergo profound changes when exposed to offspring odors at parturition. These changes in synaptic circuitry contribute both to maternal responsiveness to these odors and to their memorization. (C) 2009 Elsevier B.V. All rights reserved.