This book presents the results of a practical analysis on the potential of Geographic Information Systems (GIS) to support Strategic Environmental Assessment (SEA) processes in spatial planning. The development of an integrated GISEA approach, and its application to a number of SEAs in the Republic of Ireland, demonstrated that GIS facilitate the process by enhancing understanding of environmental and planning considerations, and improving the accuracy of assessments. The results also revealed that framework and procedural difficulties to its effective application remain.