When preparing and storing a primitive list in a tile-based graphics processing system, a first block of memory space is allocated for storing the primitive list. When there is insufficient space in the first block of memory space to store all of the graphics primitives for the primitive list, a next block of memory space to be used for storing the primitive list is allocated for storing the primitive list. An indication of the location in memory of the allocated next block of memory space is written at the beginning of the first block of memory space.