Due to the popularity of electronic commerce and the maturity of wireless technology, mobile users can access the Internet anytime anywhere without having to physically hook up any access point. To be able to manage and manipulate data downloaded from the Internet, there is a strong need for developing mobile database systems for mobile devices. Therefore, in the paper, we designed and implemented a mobile database system for Java phones. XML is adopted to describe databases. In addition, XSLT is used to define processing rules for databases so that only a general processor is required to process databases of different schemata. It is demonstrated that the proposed mobile database system is portable and interoperable. D 2004 Elsevier B.V. All rights reserved.