Linguistic and cognitive profiles were examined in 18 children with autism and 18 children with fragile X syndrome (mean ages = 34 months). State-of-the-art diagnostic procedures for autism symptom identification were administered. Eight children with fragile X met criteria for autism. Comparison of linguistic and cognitive profiles (autism, fragile X without autism, fragile X with autism) revealed that children with fragile X (with autism) were more impaired in nonverbal cognition and expressive language. Receptive language was a relative strength for children with fragile X (without autism). There were no differences in receptive language in children with autism, regardless of fragile X status. Low receptive language may be a marker for autism symptoms in young children with fragile X.