Although occurrence of disasters cannot be prevented completely, it is possible to minimize their hazards by taking precautions and applying effective emergency response plans. In addition to measures taken to reduce economical and human losses, an environmental dimension is required in these plans to control environmental pollution and lessen possible adverse effects on both ecosystems and human health, which in the long term may cost much more than direct disaster losses. Technological accidents triggered by natural disasters are one of the most important factors increasing the environmental damage. Therefore, it is of utmost importance to prepare regional plans considering both natural and technological disasters and aiming the coordination and resource sharing between the related authorities, institutions and factories. Geographical Information Systems (GIS) are powerful tools having comprehensive data query, analysis, and visualization capabilities, and they may facilitate preparation of such emergency plans. In this paper, the role of GIS in emergency response plans is explained. A case study from Turkey utilizing GIS extensively for regional environmental emergency planning is given and problems that can be faced in developing countries are discussed.