Disturbances in the development of joint attention behaviors and the ability to share affect with others are two important components of the social deficits of young autistic children. We examined the association of shared positive affect during two different communicative contexts, joint attention and requesting. The pattern for the normal children was one of frequent positive affect displayed toward the adult during joint attention situations. Compared to the normal children, the autistic children failed to display high levels of positive affect during joint attention whereas the mentally retarded children displayed high levels of positive affect during requesting as well as joint attention situations. These results lend support to the hypothesis that the joint attention deficits in autistic children also are associated with a disturbance in affective sharing.