The grid computing paradigm emerged recently as a new field distinguished from traditional distributed computing because of its focus on large-scale resource sharing and innovative high-performance applications. The grid infrastructure ties together a number of Virtual Organizations, that reflect dynamic collections of individuals, institutions and computational resources. Flexible, secure and coordinated resource sharing among VOs requires the availability of an information rich environment to support resource discovery and decision making processes. The Globus Toolkit provides applications developers with the Monitoring and Discovery Service (MDS) to support development of grid-aware applications, able to exploit the knowledge about current grid status and configuration to adapt themselves to changes in heterogeneous, dynamic environments. In this paper we describe the design and implementation of the GridLab Information Service.