It has been recognised for some time that whilst high-power lasers are suitable for cutting, welding and heat treatment, different beam mode may be required for optimum use in a particular process. However, up to now industrial lasers have generally been designed to provide only one mode. Typically this has been TEM00 at powers up to 1 kW, TEM01* at 1 - 3 kW and Multimode at 3 - 5 kW. This paper, however, describes the development of a modular industrial laser with rated powers from 1.5 to 6 kW, with a novel optical design which allows user selection of beam mode. TEM0 ' in cutting, and Multimode are all available from this laser design for optimum efficiency in cutting, welding and heat treatment applications. Further, the modular construction technique allows a user to upgrade the maximum power of his system from 1.5 kW to 6 kW to any time after installation.