XML documents are semistructured and the structure of the documents is embedded in the tags. Although XML documents can be accompaniedby a DTD that defines the structure of the documents, the presence of a DTD is not mandatory. The difficulty in deriving the DTD for XML documents lies in the fact that DTDs are of different syntax as XML and that prior knowledge of the structure of the documents is required. In this paper, we introduce DTD-Miner, an automatic structure mining tool for XML documents. Using a Web-based interface, the user will be able to submit a set of similarly structured XML documents and the system will automatically suggest a DTD. The user is also able to further refine the DTD generated to reduce the complexity by relaxing some the rules used in the system.