Visualizing large unstructured grids is extremely useful to understand natural and simulated phenomena. However, informative volume visualization is diffcult to achieve efficiently due to the huge amount of information to process. In this paper, we present a method to efficiently tessellate on a GPU large unstructured tetrahedral grids made of millions of cells. This method avoids data redundancy by using textures for storing most of the needed data; textures are accessed through vertex texture lookup in the vertex shading unit of modern graphics cards. Results show that our method is about 2 times faster than the same CPUbased extraction, and complementary with previous approaches based on GPU registers: it is less efficient for small grids, but handles millionstetrahedra grids in graphics memory, which was impossible with previous works. Future hardware evolutions are expected to make our approach much more efficient.