A graphics processing pipeline includes a vertex transformation stage 14 having a vertex transformation cache 20. If a request to transform vertex data is received and the vertex transformation cache 20 indicates that the transformed vertex data for that received request has already been generated, then a pointer to that previously generated transformed vertex data is output within a result data stream in place of the transform vertex data. The transform vertex data is stored to a memory 10 before being retrieved as required by a rasterization stage 16.