Abstract– The objective of this paper was to employ a functional linguistic approach to explore pragmatic failure in the spontaneous speech of subjects with pervasive developmental disorders (PDD). Patterns of intonation use were compared among subjects with Asperger's syndrome (AS), high-functioning autism (HFA), and psychiatric out-patient controls (OPC) with a variety of non-specific social problems. Written transcripts and audio-recordings were used to measure rates of various intonation types relative to the amount of speech produced. The major finding of the study was that the HFA subjects less often tend to employ useful patterns of intonation for communication than the AS or OPC groups. This suggests that HFA either send random intonation signals to hearers or else demonstrate systematic misuse of the linguistic system. AS subjects differed little from the controls. The implications of these results for understanding the communicative failure of PDD subjects is discussed.