The L4 and L5 dorsal root ganglia were studied in untreated rats and rats subjected to unilateral transection of the sciatic nerve, using the indirect immunofluorescence technique and antibodies to the peptide galanin (GAL). In control rats only low numbers of small ganglion cells contained GAL-like immunoreactivity (LI). After axotomy a marked increase in the number and intensity of GAL-immunoreactive ganglion cell bodies was seen on the lesion side. Thus, some primary sensory neurons react to transection of their peripheral branches by expressing increased GAL levels. A similar reaction has been described by other groups for vasoactive intestinal polypeptide.