Laser transmission welding is frequently being used increasingly for joining complex, assembly-oriented components, thanks to its small heat affected zone. As a result of the cooling processes, residual stresses can develop inside the components, potentially leading to stress cracking and premature component failure. One subgoal of process design should therefore be to reduce the level of residual stresses as far as possible when laser welding is employed. This work looks into experimental testing for residual stresses, as a factor for the weld parameters in quasi-simultaneous laser transmission welding, with the objective of determining the optimum welding parameters. The ARAMIS optical measuring system for deformation analysis was used to this end, in conjunction with a modified hole-drilling method. POLYM. ENG. SCI., 50:1520-1526, 2010. (C) 2010 Society of Plastics Engineers