Whether or not the Golgi apparatus is a unique organelle with an identity discrete from the endoplasmic reticulum (ER) is a question that has occupied many cell biologists in recent years. In an article in the March 2002 issue of this journal, I discussed some recent papers claiming that structural Golgi proteins are dynamic and recycle continuously via the ER [1xThe Golgi apparatus: going round in circles?. Barr, F.A. Trends Cell Biol. 2002; 12: 101–104Abstract | Full Text | Full Text PDF | PubMed | Scopus (15)See all References[1]. Now, Warren and coworkers provide biochemical evidence for the alternative point of view that substantiates previous work showing that structural Golgi proteins such as GM130 are not associated with the ER in either mitotic cells or cells treated with the drug brefeldin A [2xPartitioning of the matrix fraction of the Golgi apparatus during mitosis in animal cells. Seemann, J et al. Science. 2002; 295: 848–851Crossref | PubMed | Scopus (95)See all References[2]. Interestingly, the Golgi enzyme N-acetylglucosaminyltransferase I does cofractionate with an ER marker in BFA-treated cells, indicating that enzymes and structural proteins do not behave in the same way. The authors conclude from this that it is structural proteins such as GM130 that define the Golgi apparatus and give it a unique identity in both interphase and mitosis rather than enzyme-containing membrane structures.