Although the term deaf-blind implies a complete absence of hearing and sight, in reality, it refers to children with varying degrees of vision and hearing losses. The type and severity differ from child to child. The key feature of deaf-blindness is that the combination of losses limits access to auditory and visual information. Children with deaf-blindness require teaching methods that are different from those for children who have only hearing or vision loss. When both vision and hearing are affected, especially from birth or early in life, natural opportunities to learn and communicate can be severely limited. More than 90% of children who are deaf-blind have one or more additional disabilities or health problems and some may be identified as having multiple disabilities rather than deaf-blindness. In these cases, the impact of combined hearing and vision loss may not be recognized or addressed. This paper provides details about the population of children who are deaf-blind, including the classification of vision and hearing loss, the types of additional disabilities that may be present, and the causes of deaf-blindness.