This dissertation research will investigate how autism affects sign language in deaf children on the autism spectrum. There is a significant population of children with autism at schools for the deaf around the country, yet until now their language development has received little attention from researchers. The signing of approximately 40 autistic children enrolled at deaf schools in Massachusetts, Ohio, Iowa, Texas, and Oregon will be videotaped and analyzed. Through observations of interactions with teachers and classmates at school, as well as a sign elicitation test, the signing of these children will be compared with that of hearing autistic children who are being exposed to sign in addition to speech, as well as the signing of typically-developing deaf children. The project will test the hypothesis that the acquisition of sign language may pose specific challenges to children with autism. In particular, sign languages require learners to take the physical perspective of others in order to imitate and successfully reproduce signs, something that is not necessary for children acquiring spoken languages. This perspective-taking may be impaired in autism, leading to problems in sign language that are characteristically different from the problems found in autistic speech. A systematic analysis of deaf autistic children's signing could reveal particular points of difficulty and ultimately lead to improved assessments, interventions, and teaching strategies for autistic children.