To study the functional role of endogenous basic fibroblast growth factor‐2 (FGF‐2) during degeneration and regeneration of the sensory system, we have determined the expression and regulation of FGF‐2 and FGF receptor (FGFR)‐1 mRNAs in spinal ganglia and sciatic nerve during experimental transection and crush injury of the sciatic nerve. In contrast to levels of the FGFR‐1 transcript, which is not altered, the level of FGF‐2 mRNA is dramatically up‐regulated in spinal ganglia after injury. In the proximal and distal nerve stumps both transcript levels are significantly elevated, albeit at different time points. The FGF‐2 isoforms are differently up‐regulated in spinal ganglia and sciatic nerve following peripheral nerve lesion. The differential response of FGF‐2 mRNA and protein and of FGFR‐1 mRNA in spinal ganglia and sciatic nerve after lesion is suggestive of different physiological functions: a local reaction at the lesion site where axonal regrowth occurs and a trophic reaction for the degenerating/regenerating sensory neurons.