Abstract: Provided is a multi-tiered cascading crawling system for finding on a network information related to one or more predetermined topics or subtopics of interest. In general, embodiments of the present invention provide a system that operates in multiple “tiers,” where at least some of the output of one tier is used to comprise the input of the next tier. Each tier generally analyzes collections of documents on the network using successively more restrictive criteria about the subject matter of each collection and/or about which collections may be related to the one or more topics or subtopics. In general, only the final tier performs an exhaustive crawl of all of the documents of the collections that are identified by the system as being relevant to the topic or subtopic of interest.