The objective of this report is to give an introduction to the subject of cooperative systems and an overview of projects related to cooperative systems. Issues related to cooperative systems are also discussed in the report. Two areas of great importance for cooperative systems are the standardization process of cooperative systems in Europe and the communication frequency used for cooperative systems. These two subjects are therefore discussed in more detail in the report. The report has been focusing on cooperative systems, which is a part of the wider concept Intelligent Transport Systems (ITS). The 'traditional' Intelligent Transport Systems use technology, inside or outside of the vehicle, to give the driver some kind of information. The driver gets the opportunity to act upon the given information. Along with the increased amount of new technology the use of information and communication in the transport area has increased. Today cooperative systems are well-known in the transport area. The idea is to extend the more traditional Intelligent Transport Systems and build systems that are able to communicate with each other. These systems could be located inside the vehicle or as a road-side unit outside of the vehicle. The benefit with cooperative systems is the ability to send and receive real-time information and to use this information in order to increase safety, efficiency and environmental impacts on the roads.