This dissertation represents the first systematic study of the sign language of deaf children with autism. The signing of such children is of particular interest because of the unique ways that some of the known impairments of autism are likely to interact with sign language. In particular, the visual-spatial modality of sign requires signers to understand the visual perspectives of others, a skill which may require theory of mind, which is thought to be delayed in autism (Baron-Cohen et al., 1985). It is hypothesized that an impairment in visual perspective-taking could lead to phonological errors in American Sign Language (ASL), specifically in the parameters of palm orientation, movement, and location. Twenty-five deaf children and adolescents with autism (10 deaf-of-deaf and 15 deaf-of-hearing) between the ages of 4;7 and 20;3 as well as a control group of 13 typically-developing deaf-of-deaf children between the ages of 2;7 and 6;9 were observed in a series of studies, including naturalistic observation, lexical elicitation, fingerspelling, imitation of nonsense gestures, two visual perspective-taking tasks, and a novel sign learning task. The imitation task was also performed on a control group of 24 hearing, non-signing college students. Finally, four deaf mothers of deaf autistic children were interviewed about their children’s signing. Results showed that young deaf-of-deaf autistic children under the age of 10 are prone to making phonological errors involving the palm orientation parameter, substituting an inward palm for an outward palm and vice versa. There is very little evidence that such errors occur in the typical acquisition of ASL or any other sign language. These results indicate that deaf children with autism are impaired from an early age in a cognitive mechanism involved in the acquisition of sign language phonology, though it remains unclear which mechanism(s) might be responsible. This research demonstrates the importance of sign language research for a more complete understanding of autism, as well as the need for research into atypical populations for a better understanding of sign language linguistics. / text