The report includes the Proceedings of the International Symposium on Catastrophic Tunnel Fires held in Borås, Sweden, 20 – 21 of November 2003. It provides unique data from the large-scale tests performed in the Runehamar Tunnel 2003 under leadership of SP in co-operation with TNO in the Netherlands and SINTEF in Norway. It also includes presentations of various catastrophic tunnel fires, rescue and fire fighting in tunnels and passive and active fire protection of tunnels. The European research project UPTUN and the new EU regulations for road tunnels are presented as well. Over 200 people from over 20 countries attended this symposium.