A tile-based graphics system has a rendering space sub-divided into a plurality of tiles which are to be processed. Graphics data items, such as parameters or texels, are fetched into a cache for use in processing one of the tiles. Indicators are determined for the graphics data items, whereby the indicator for a graphics data item indicates the number of tiles with which that graphics data item is associated. The graphics data items are evicted from the cache in accordance with the indicators of the graphics data items. For example, the indicator for a graphics data item may be a count of the number of tiles with which that graphics data item is associated, whereby the graphics data item(s) with the lowest count(s) is (are) evicted from the cache.