Abstract: A method of production of a rotor blade (15) for wind turbine generator (WTG) is disclosed using a load carrying structure or spar (10) extending from the root end of the rotor blade (15) towards the tip end of the rotor blade (15), and comprising: applying pre-shaped foam members (11 and 12) to the load carrying structure or spar (10) to build up a desired outer blade configuration, removing or adding foam material to obtain a desired outer blade configuration, coating the outer surface of the rotor blade with a material providing a smooth and rigid surface shell (16) structure, and finishing the outer surface shell (16) of the rotor blade (15) by grinding and optionally painting. Using only relative simple provisions a considerably more flexible manufacturing process is achieved with important advantages regarding the outer configuration of the rotor blades.