A case study analyzed the echolalia behavior of an autistic 11-year-old boy, based on recordings made in his home and school. Focus was on the subset of immediate echolalia referred to as pure echoing. Using an approach informed by conversation analysis and descriptive phonetics, distinctions are drawn between different forms of pure echo. It is argued that one of these forms, "unusual echoes," has distinctive interactional and phonetic properties that do not have a counterpart in the speech of non-autistic children. These consist principally of a particular segmental and suprasegmental relationship to the prior adult turn, a particular rhythmic timing and a functional opaqueness. This behavior is set within the context of this child's general communicative behavior, which, in various ways, places a premium on the use of repetition in unusual echoes, although here the interactional and phonetic properties of such repetitions suggest that they display a distinct interactional stance to the questions that precede them. Contains 25 references. (Author/MSE)