The present work deals with the grain refinement of Zr-alloyed Al-Mg-Si alloys. Although alloys of this class show many positive properties such as good weldability, strength and high processability, the addition of zirconium creates a disadvantageous, very coarse casting structure. It is known from the literature that Zr causes inactivation of the grain refiner, which causes an enormous increase in the grain size. The underlying mechanism has not yet been unequivocally clarified. In addition to a critical examination of the possible processes in Zr- containing alloys of this type, the first part of this work contains a summary of the mechanisms of solidification and grain refinement in general. Building on this, a total of twelve tests were carried out with the aim of achieving a fine-grained structure. On the one hand, industrial raw material was used (EN AW-6082), which was remolded and alloyed with Zr. On the other hand, a build-up melt based on primary Al (99.92% by weight Al) was used, which was adapted to the composition mentioned above. Two different grain refiners (Al-5Ti-1B and Al-3Ti-0.15C) were tested on these two melts with different addition amounts. The results are summarized below. Remolded industrial raw material without Zr shows no strong dependence on the further addition of Al 5Ti-1B due to the grain refinement already carried out by the manufacturer. In all melts there is a large coarsening of the grain due to the addition of Zr. Both Al-5Ti-1B and Al- 3Ti-0.15C show a similarly positive effect. While there is a decrease in the refining effect in the case of both grain refiners over the period of 60 minutes, this occurs more markedly in the carbon-based material. By adding elemental Ti or increasing the amount of Al-5Ti-1B, it is possible to achieve sufficient grain refinement. A variation of Fe or Mn in combination with a Zr addition shows no measurable influence on the grain size.