Autism and the related pervasive developmental disorders are a heavily researched group of neurodevelopmental conditions. In addition to core symptoms, there are a number of other physical and motor conditions that co-occur at high rates. This paper provides a review of factors and behaviors that correlate highly with disorders on the autism spectrum. Among these conditions are premature birth, birth defects, gross and fine motor skills, and obesity. Each of these topics is addressed, and what researchers have found are presented. These data have important implications for the types of collateral behaviors that should be assessed and treated, along with the core symptoms of autism.