Flexible voice recognition units are currently available as an add-on for popular microcomputers. These systems provide an opportunity to prototype speech dialogues for proposed products or services. This type of prototype can be useful in two ways. Firstly, to investigate the design of speech-based interfaces employing behavioural experimentation to quantify the effects on user attitude and performance of variations in interface design. Secondly, as a focus for discussion and informal evaluation within a design project producing a specific product or service.