Fragile X syndrome is a newly recognized X-linked disorder which has been associated with a high prevalence of psychiatric disturbance, particularly attention deficit disorder and autism. The present study involved the neuropsychiatric evaluation of 14 males with the disorder who were between the ages of 3 to 27 years. Pervasive hyperactivity, impulsivity, and attentional deficits were found among all of the subjects, while a significant degree of anxiety was manifested by more than half. Although the majority of subjects exhibited poor eye contact, atypical speech and language functioning, and stereotyped behavior, only one met DSM-III diagnostic criteria for a persistent pervasive developmental disorder. Gaze aversion, noted among half of the subjects, was attributed to underlying anxiety rather than to autistic social dysfunction because of the otherwise socially engaged and affectionate behavior exhibited by the subjects. Failure to make this distinction in the context of cognitive and linguistic impairments associated with fragile X syndrome may account for the high rates of autism reported by other investigators.