Autism spectrum disorders (ASDs) are life-long developmental disorders characterized by impairments in the development of reciprocal social and communication skills, abnormal language development, and a restricted repertoire of behaviors and interests. While it has been known for some time that children with ASD can evince elevated rates of anxiety symptoms, little research has been conducted on whether deficits in communication skills affect the range of anxiety symptoms in infants and toddlers with ASD. This study represents a first attempt to determine whether deficits in communication skills have an effect on the expression of anxiety in infants and toddlers with autistic disorder and pervasive developmental disorder-not otherwise specified. Seven hundred thirty-five infants were evaluated with respect to the nature and extent of anxiety symptoms and developmental functioning. Both receptive and expressive communication skills appeared to play a significant role in the manifestation of anxiety symptoms. (Contains 3 figures and 4 tables.)