Abstract: This invention provides methods apparatus and data structures useful for mining databases for frequent items. The invention uses a frequent pattern tree to represent the contents of a database in a manner which is conducive to data mining. The frequent pattern tree tends to be smaller than the original database. A frequent pattern tree can be mined recursively. The frequent pattern tree and associated methods and apparatus of this invention is relatively fast, efficient and scalable and can be used to mine both long and short frequent patterns.