Fast and accurate speech recognition systems bring with them the possibility of designing flexible voice driven applications. In this paper, we highlight the needs related to a voice interface and describe the implementation of a general-purpose spoken language interface, the Camegie Mellon Spoken Language Shell (CM-SLS). CM-SLS provides voice interface services to different applications running on the same computer. CM-SLS was used to build the Office Manager, a collection of applications that includes an appointment calendar, a personal database, voice mail and a calculator. The performance of several system components is described.