In this talk, I will address challenges and opportunities in voice search systems. I will also talk about a couple related projects and their research findings and implications for voice search system design. Earlier research indicates that users of information systems employed voice search much less frequently than keyboard search because they disliked the system mistakes and the fact that they were unable to modify the queries. We found that in keyboard search, query reformulation is facilitated by partial query modification, which is not supported by most of the current voice search systems. Users need to speak complete query in voice search even with minor changes. We examined partial query modification during voice search through a Wizard of Oz user experiment.