The XML (eXtensible Mark-up Language), proposed by the W3C (World Wide Web Consortium) as the new standard for data representation and exchange in the Internet, is a document mark-up (meta) language that seems adequate to the needs of today's World Wide Web. With the proliferation of XML documents in the Web, it is necessary to store and query them efficiently. It is our purpose to investigate the different approaches currently available to the storage and management of XML data. Moreover, we intend to analyse the main characteristics of some of the XML query languages, which have been proposed both by the database and Internet communities, namely XML-QL, XQL, Quilt, and Xquery. The latter has been proposed by the W3C Query Working Group with the purpose of providing a standard for a XML query language. We believe that a query language such as Xquery will certainly accelerate the utilization of XML as an alternative approach to data storage, since it will make possible to interrogate, efficiently and in unpredictable ways (queries ad hoc), XML documents.