General-purpose search engines such as AltaVista and Lycos are notorious for returning irrelevant results in response to user queries. Consequently, thousands of specialized, topic-specific search engines (from VacationSpot.com to KidsHealth.org) have proliferated on the Web. Typically, topic-specific engines return far better results for "on topic" queries as compared with standard Web search engines. However, it is difficult for the casual user to identify the appropriate specialized engine for any given search. It is more natural for a user to issue queries at a particular Web site, and have these queries automatically routed to the appropriate search engine(s). This paper describes an automatic query routing system called Q-Pilot. Q-Pilot has an off-line component that creates an approximate model of each specialized search engine's topic. On line, Q-Pilot attempts to dynamically route each user query to the appropriate specialized search engines. In our experiments...