Recent research in childhood autism has provided support for the hypothesis that a central cognitive deficit involving severe language impairment underlies this disorder. In this study a group of autistic children were tested for handedness and for lateralization of speech function using a dichotic listening task. Contrary to earlier reports there were no left-handed children in the group although a number showed mixed preference. In the dischotic listening task using pairs of single syllable words the autistic group performed similarly to a matched group of normal children in terms of numbers of correct responses but over all did not show the right ear advantage characteristic of the normal children. There was a significant excess of right hemisphere dominance for verbal stimuli amongst the autistic children suggesting that for some at least, language functions had developed in the right hemisphere. Lateralization was shown to be related to presence or absence of speech before the age of 5 years and to IQ level.