Deafness affects roughly 2/1000 new-borns and is one of the most common congenital impairments. Newborn hearing screening, also implemented in Korea, has decreased the age at diagnosis of congenital hearing loss. Although newborn hearing screening has increased the identification of single-sided deafness (SSD) or asymmetric hearing loss (AHL), caregivers of children with SSD/AHL are often hesitant to seek for adequate therapy. In these cases, the consequence will be a failure to intervene until long after major negative developmental effects have occurred, which results in significant negative clinical implications. Also, screening programs cannot cover children who acquire SSD or AHL from postnatal infection, trauma, or worsening of preexisting AHL. Although the prevalence of SSD/AHL in neonates varies from 0.45 to 2.7 in 1000 new births, it increases up to 30 – 56 in 1000 school-aged children. Also, although bilateral profound hearing loss is conventionally treated with cochlear implantation (CI), considering that still only 1 ear is implanted in most cases, CI yields, in effect, children with acquired SSD in most cases. Recent studies on SSD both in animal models and in children have consistently shown evidence of an “aural preference syndrome” in which SSD in early childhood reorganizes the developing auditory pathways toward the hearing ear, with weaker central representation of the deaf ear. In this regard, this talk will summarize evidences from well-established animal models and functional brain imaging in human subjects with regard to biological, functional, and behavioral developments of the central auditory pathway to underscore effects of SSD/AHL in children. By summarizing recent studies, we may be able to reconfirm the importance of early intervention using auditory prostheses, including hearing aids and cochlear implants, within a sensitive period in development in children with SSD/AHL.