The ESA SPace ENVironment Information System (SPENVIS) provides standardized access to models of the hazardous space environment through a user-friendly WWW 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. It is available on-line at http://www.spenvis.oma.be/spenvis/. Intranet versions are also available. SPENVIS has been operational for about three years, with a continuously expanding user community and set of functions. 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 with the models 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. It is very useful in conjunction with radiation effects and electrostatic charging testing in the context of hardness assurance. SPENVIS is based on internationally recognised standard models and methods in many domains. It uses an ESA-developed orbit generator to produce orbital point files necessary for many different types of problem. It has various reporting and graphical utilities, and extensive help facilities. SPENVIS includes models of the radiation environment and effects, including NIEL and internal charging. It also contains an active, integrated version of the ECSS Space Environment Standard, and access to in-flight data. Apart from radiation and plasma environments, SPENVIS includes meteoroid and debris models, atmospheric models (including atomic oxygen), and magnetic field models implemented by means of the UNILIB library.The UNILIB library implements a series of tools for coordinate transformations, magnetic field computations, magnetic coordinate evaluation, magnetic field line tracing and drift shell tracing. The UNILIB library was originally designed as a tool for the ESA/ESTEC TREND project (Trapped Radiation ENvironment Development) to investigate new coordinates to organise trapped particle fluxes, but can be applied to other fields of magnetospheric research. For instance, UNILIB determines mirror point and footpoint locations and evaluates adiabatic invariants. The UNILIB library is freely accessible from the Web (http://www.magnet.oma.be/unilib/) for downloading in the form of a Fortran object library for different platforms (DecAlpha, SunOS, HPUX and PC/MS-Windows). An interface for the Interactive Data Language (IDL) is included in the distribution. The Web site features extensive documentation including installation instructions, a reference guide, programme examples, and frequently asked questions. A news group has been established at news://news-ae.oma.be/unilib.