Proanthocyanidin-A2, a catechic dimer extracted from the bark of Aesculus hippocastanum L., was tested on peripheral nerve regeneration. Reinnervation of EDL and soleus muscles following traumatic nerve damage was investigated in rats by using "in vivo" tension recording technique. Muscle contraction force (twitch and tetanus), the number of motor units and the time course of twitch (time to peak and half relaxation time), were observed. The results obtained do not show that the time course of EDL and soleus muscles reinnervation is different in Proanthocyanidin-A2-treated rats in comparison to control animals. On the contrary, results point out an increase in EDL and soleus muscle mass, both in denervated and in undenervated treated rats compared to corresponding controls. Moreover, consistently with this finding, an increase in their contraction force was found. These data show that Proanthocyanidin-A2 exerts a trophic effect on muscle.