Using the indirect immunofluorescence technique, the distribution of Ca²⁺/calmodulin-dependent protein kinase IV (CaM kinase IV) was studied in dorsal root ganglia (DRGs) and the sciatic nerve under normal circumstances and after axotomy and nerve ligation. CaM kinase IV-like immunoreactivity (-LI) was observed mainly in small DRG neurons but also in some large ones with the immunoreactivity mainly confined to the cell nuclei and with varying levels in the cytoplasm. CaM kinase IV-LI was present in around 1 4 of all CGRP-positive neurons and in the vast majority of the somatostatin-positive neurons. The enzyme levels decreased markedly after axotomy. The enzyme was also observed in axons in the sciatic nerve and accumulated both proximal and distal to a ligation. The present results suggest that CaM kinase is not of direct importance for upregulation of neuropeptides in DRG neurons after nerve injury. In addition to a nuclear function it may also play a role in the peripheral processes of DRG neurons.