In nerve cells, the waxy molecule ceramide plays roles in both cellular differentiation and death, but a new study shows those roles could vary based on how ceramide is formed. Ceramide is generated via 3 pathways: newly from palmitoyl-CoA and serine, from the breakdown of sphingomyelin, and through the endosomal salvage pathway. Experiments showed that blocking ceramide synthesis did not alter ceramide levels in PC12 cells, which require nerve growth factor (NGF) to survive and differentiate, but blocking synthesis did decrease ceramide levels in TrkA cells, which differentiate spontaneously. Blocking sphingomyelin breakdown, however, inhibited differentiation and reduced ceramide in both cell lines. Without NGF, PC12 cells begin to atrophy and die, and preventing sphingomyelin breakdown did not protect them, but it did suppress rising ceramide levels to some degree versus controls. In contrast, blocking ceramide synthesis dramatically reduced cell death in PC12 cultures deprived of NGF and suppressed the rise in ceramide levels. Overall, this study suggests that in both PC12 and TrkA cells, differentiation is driven by sphingomyelin-derived ceramide, and when NGF is removed and PC12 cells begin to die, ceramide is derived from both pathways. Interestingly, however, apoptosis depends largely on newly synthesized ceramide.