Functional recovery after nerve crushing was investigated in the following manner: Under pentobarbital anesthesia the sciatic nerve of the rat was crushed at the level of the hip (proximal crush) or the thigh (distal crush). The recovery processes after the nerve crushing were followed by measuring distances between the first and fifth digits(DBD.1 approximately 5) and between the second and fourth digits (DBD.2 approximately 4) of the hind paw, and by observing changes in "behavior" scored on a scale of 10 according to the degree of behavioral disorder of the hind paw and leg. Results obtained by these methods showed good reproducibility. The DBD values and the scores for behavior recovered significantly faster after weak nerve crushing than after strong crushing, and after distal rather than after proximal crushing. When a segment of the sciatic nerve was resected, there was no recovery. These results suggest that DBD.1 approximately 5, DBD.2 approximately 4, and the behavior observed in these experiments serve as good indices for evaluating the degree of functional recovery after nerve injury in unanesthetized and unrestrained animals. Effects of a preparation of vitamins B1, B6, and B12 (B complex) on these three parameters and on weights of 9 muscles of the hind leg were also studied. These studies showed that the B complex facilitated functional recovery from nerve injury faster than its components, and that on muscle atrophy the B complex had its most effects on the soleus. It was also shown that B1 and B12 by themselves had significant facilitating effects on the functional recovery.