Caregivers of 55 boys with fragile X syndrome (ages 3-12) and 57 matched controls completed five behavioral questionnaires. Principal components analysis yielded 5 behavioral clusters: abnormal language, tactile defensiveness, poor self-control, poor eye contact/shyness, and hand flapping. Boys with fragile X were four times more likely to have both tactile defensiveness and abnormal language. (Author/JDD)