Laser welding is emerging as one of the most interesting methods for joining of metals. The process has already been proven in both high quality welding in aerospace, electronics and medical engineering as well as in applications for high volume production in automotive industry. Over the past decade a substantial amount of theoretical research has been carried out into the subject of deep penetration laser welding. Many of the models developed for the laser welding process, are highly sophisticated and demand the work of scientists for performing the modelling and interpretation of the modelling results. There is a substantial lack of "easy-to-use" models which can be handled by research and development engineers in the manufacturing industry and which will give such important data as the geometrical size and form of the welded joints. The over all objective by this work was to develop a fast and user-friendly model for the prediction of weld geometries in various engineering materials, different joint types and wavelengths in laser welding. A basic, analytical thermodynamic model, first developed by A. Kaplan and then further by C. Lampa, was expected to be a suitable base for continuing development of a laser welding model, which could be used for real joint configurations and various engineering materials, as well as for both CO2- and Nd:YAG-lasers. The project has succeeded in developing this analytical model, "The Luleå model for laser welding simulation", for predicting the geometrical dimensions of laser welds in overlap and butt configuration. The metals supported by the model are mild steels, stainless steels, aluminium alloys and titanium alloys. Welding of those materials can be simulated by using CO2- or Nd:YAG laser. A PhD-degree and a substantial amount of scientific results for a docent degree have also been achieved by this work. The analytical model has been given a user-friendly interface and is incorporated on a CD for easy access. Through the software interface, the material properties and process parameters can be changed to the liking of the user. Calculated results in form of weld shape as a function of process speed are offered and compared to experimental macrographs. The "Luleå model for laser welding simulation", was in its basic state originally developed for ELANET, the "EuroLaser Academy Network for Educational Tools". The objective of the ELANET is to make use of the numerous theoretical investigations in laser materials processing carried out in the past. Developed models, including "the Luleå model" shall be implemented into a CD for easy accessibility and distribution. The simple structure of the calculation logic of this analytical model does not require high performance computer sources. The "Luleå model for laser welding simulation" is therefore suitable for use directly on a shop floor on a standard equipped personal computer. The introduction and implementation of the model to the industry is planned to take place during year 2001 when the model will be presented and used in practical industrial tests.