Resource discovery in a Grid environment is a critical problem, as a typical Grid system includes a very large number of resources, which must be readily identified and accessed to run applications. Traditional Grid discovery algorithms perform poorly, as they do not scale, nor allow Grid-enabled applications to transparently query the whole set of Grid resources. Peer-to-Peer (P2P) has been argued as a suitable distributed paradigm that not only overcomes the issues of scalability of such discovery systems, but also better supports the discovery of resources in a context of dynamicity of resources and associated information. In this paper we propose a P2P system for indexing and discovering Grid resources. We assume that Grid resources are characterized by a set of attributes, and our system can be queried for resources satisfying arbitrary range conditions on these attributes. Note that traditional P2P searching techniques can not be directly applied in this case, since they work w...