Following nerve injury, modified somatic ion channels may underlie ectopic activity in axotomized A-type neurones in dorsal root ganglia (DRGs) leading to abnormal pain signalling. Using intracellular microelectrodes both in vivo and in vitro, action potentials (APs) were recorded in rat DRG neurones classified by axonal conduction velocity. After lesions to L5 spinal or sciatic nerves, APs in both A alpha/beta and A delta cells were wider, and those in A alpha/beta neurones more frequently showed inflections during repolarization, than APs in cells in undamaged ganglia. AP amplitudes and dV/dt(max) were not significantly altered by axotomy. These results confirm previous observations in intact ganglia in vitro but differ from those reported for dissociated neurones using patch recording techniques.