Forty-one children with sex chromosome anomalies identified from the chromosome screening of a newborn population were blindly evaluated by a speech-language pathologist, along with a control group of 31 siblings. 47,XXX girls and 47,XXY boys were found to have increased problems in auditory perception, receptive language, and expressive language; the problems of the 47,XXY boys were less severe than those of the 47,XXX group, and reflected specific deficits in their ability to process linguistic information rather than a deficit in comprehension. An increased occurrence of speech production problems among the 45,X girls was associated with the presence of oral/structural malformations that often had no measurable effect on their production of speech sounds. Although the 45,X girls and 47,XYY boys had no significant increase of problems in auditory reception, receptive language, and expressive language, the trend of the data suggested more difficulty than in the control groups. The mosaic children were not different from the control subjects. Some children in all groups were found to have normal speech and language development.