ESA's Space ENVironment Information System (SPENVIS) provides standardized access to models of the hazardous space environment through a user-friendly World Wide Web interface. The interface includes parameter input with extensive defaulting, definition of user environments, streamlined production of results (both in graphical and textual form), background information, and on-line help. The system can be accessed at the WWW site http:l/www.spenvis.oma.be/spenvis/.Intranet versions are also available, and a new Java based server/client system is in the final stages of development. SPENVIS Has a continuously expanding international user community (over 450 registered users), and its set of models and functionalities is continually increased. SPENVIS Is designed to help spacecraft engineers perform rapid analyses of environmental problems and, with extensive documentation and tutorial information, allows engineers with relatively little familiarity to produce reliable results. It has been developed in response to the increasing pressure for rapid-response tools for system engineering, especially in low-cost commercial and educational programmes.