The Intention of this study was to examine and compare the effect of three different polymerization systems on the dimensional changes of denture-resin. The development of the fissure has been measured at five fixed points at the posterior border of upper complete dentures after a 4-weeks'-storage in water and saliva respectively. The perform-Inkovac-System showed the best, the SR-Ivocap-System the most unfavorable results; the conventional "stuff-press-system" gave only medium satisfaction.