Paralanguage is that part of speech which is lost in transcription to formal text. This definition includes vocal segregates, the short non-lexical utterances such as "mm-hm" and "oh!" which regulate human dialogue. The paper focuses on the role of vocal segregates in human dialogue and presents the argument that the characteristics which make them such effective features of human dialogue might also make them useful in human-computer dialogue. Two studies are described which demonstrate subjects' ability to understand these sounds in both recorded and synthesised form, out of linguistic context. Three testbed applications of vocal segregates in human-computer dialogue are also described, it is concluded that vocal segregates, if used appropriately, can streamline speech input/output dialogues and provide support for users of conventional screen-based systems. Guidelines for the use of vocal segregates in human-computer dialogue are provided. It is recommended that further studies should be conducted to investigate the short-term and long-term benefits of using vocal segregates in human-computer interfaces.