Axonal mRNA transport is robust in cultured neurons but there has been limited evidence for this in vivo. We have used a genetic approach to test for in vivo axonal transport of reporter mRNAs. We show that ß-actin's 3'-UTR can drive axonal localization of GFP mRNAin matureDRGneurons, but mice with ß-actin's 3'-UTR show no axonal GFP mRNA. Peripheral axotomy triggers transport of the ß -actin 3'-UTR containing transgenemRNAinto axons. This GFP-3'- ß -actinmRNAaccumulates in injured PNS axons before activation of the transgene promoter peaks in the DRG. Spinal cord injury also increases axonal GFP signals in mice carrying this transgene without any increase in transgene expression in the DRGs. These data show for the first time that the ß -actin 3'-UTR is sufficient for axonal localization in both PNS and CNS neurons in vivo.