In this paper, an intersection collision warning system using DGPS (Differential Global Positioning System) will be proposed. The system is developed to prevent collisions of vehicles crossing at intersections, especially at well visibility intersections without traffic lights. Two GPS receivers are installed on two vehicles on the move towards the same intersection from different directions. The position and velocity information of the vehicles are measured by on-board GPS receivers, and then transmitted from one vehicle to another by inter-vehicle communication (IVC). Therefore, the relative position and direction of each vehicle and collision judgment coefficient (CJC) which is defined by using the relative position of vehicles are calculated. After taking the crossing position of directions and the variation of CJC into account, the position of the intersection and the possibility of collision can be predicted in advance. Warning will be given to drivers with a prearranged timing.