This paper, based on observations made on 170 patients with injuries of the peripheral nerves whom we have studied at U. S. Army General Hospital No. 1, deals only with some problems which we have encountered and with the means and methods by which we have attempted to solve them. The paper concerns itself somewhat with the diagnosis of the injuries, but chiefly with the general conditions on which successful treatment must depend. We have not allowed ourselves to draw any conclusions as to the final results of the methods of treatment used as several years must elapse before conclusive data can be forthcoming. We shall, in what follows, speak of the significance of some symptoms and signs of nerve injury, of some aspects of the finer anatomic structure of the peripheral nerves, and of the anatomic basis and guiding principles for the technic of nerve suture and nerve grafting.