The present study provides in vitro and in vivo evaluation of Paeoniae alba Radix (PR) on peripheral nerve regeneration. In the in vitro study, we found the PR caused a marked enhancement of the nerve growth factor-mediated neurite outgrowth from PC12 cells as well as their expression of growth associated protein 43 and synapsin I. In the in vivo study, silicone rubber chambers filled with the PR water extract were used to bridge a 10-mm sciatic nerve defect in rats. At the conclusion of 8 weeks, regenerated nerves in the PR groups, especially at 1.25 mg ml(-1) had a higher rate of successful regeneration across the wide gap, relatively larger mean values of total nerve area, myelinated axon count and blood vessel number, and a significantly larger nerve conductive velocity compared to the control group (P < .05). These results suggest that the PR extract can be a potential nerve growth-promoting factor, being salutary in aiding the growth of injured peripheral nerve.