Searching the Web on a mobile device such as a cell phone poses unique problems for the user that cannot be easily overcome through the interface. Given the restricted display of current wireless devices, users cannot efficiently examine search results when they are presented as a long list. In our system, Hyponym, we organize search results into topics and allow the user to explore relevant resources within each topic. The data to support this kind of analysis are drawn from sequences of Web pages that users have visited while searching. We have found that queries that lead users to request similar pages tend to be topically related. From this simple observation, we form clusters or groups of queries that are used to structure the search display. Hyponym can be thought of as a collaborative filtering application that takes as its input navigation data from previous Web-searching tasks. Because of this, the lists that we return within each topic or query group tend to be much more accurate than those recommended by standard search engines. In fact, Hyponym can significantly cut the number of pages a user visits while searching the Web. We are currently extending the Hyponym framework to support personalization and location-specific information.3