ABSTRACT In order to respond rapidly and successfully to an oil spill occurring in a defined geographical area, a contingency plan which includes information and processes for oil spill containment and clean-up is required. An important part of the plan'S development, should involve evaluating oil spill risk based on the identification of vulnerable coastal environments. In this work, a methodology to determine an index that represents the oil spill vulnerability of a specific coast is developed. In order to provide a useful decision-making tool, special emphasis is given to the integration in one single index, of physical, biological as well as socio-economical aspects. To do this, three intermediate indexes which include different indicators are defined. The oil spill vulnerability index, V, is calculated by means of a weighting scheme as a result of the participation of interest groups involved in the decision-making process. The presented methodology is applied to the Cantabrian coast (Bay of Biscay, Spain) which was one of the areas most affected by the Prestige oil spill. The work is based on GIS technology allowing an efficient information management and the generation of updated oil spill vulnerability maps.