The rapid increase of GIS applications in 1990s is the result of exponential development of computer and computer related information technologies (CAD, CAM, computer graphics, remote sensing, networking etc.) as well as general increase in environmental problems awareness in their temporal, spatial and synergic aspects. Generally, three modes of GIS usage are recognized: 1. as a tool for (cartographic) output creation, 2. as a spatial database and 3. as a tool for spatial analyses and modeling. Complex environmental problems solutions often go beyond the scope of individual scientific disciplines and their global aspect is a stimulus for multinational collaboration. Due to the limits of quantitative methods in processes such as decision making or EIA, these are sometimes substituted by empirical knowledge represented in the form of logical rules integrated in expert (knowledge based) systems. Commercially available desktop GIS software as well as the existence of spatial databases at local to multinational levels is accelerating the broad spectrum of GIS applications in various environmental branches and scales. Still, a substantial amount of conceptual, technical, methodical, financial and organizational problems remains, frustrating the starting phases of a GIS application development. The rapid progress in computer technology – mainly visualization, animation, multimedia – is bringing new horizons in research as well as in education and communication with public.