Several aspects of echolalic speech produced by five autistic children were investigated. We found that the incidence of echolalia was influenced by the type of question addressed to the child and, to a lesser extent, by the child's comprehension of the specific relationships expressed in the question. Additionally, acoustic analysis showed that a substantial proportion of echoes involved a prosodic modification of the examiner's question. Further analyses indicated that some of these modified echoes represent more than just a primitive conversational strategy. Specifically, they seem to reflect a higher level of processing and serve a semantic function, that of affirming the examiner's question.