Leprosy neuropathy may develop into subacute and chronic inflammatory scenarios, called reactions, which may cause entrapments in the anatomic tunnels. Objective: This study describes the late nerve conduction findings in patients with ulnar neuropathy at the elbow that were submitted to clinical and surgery treatments. Methods: A total of 27 nerves of 21 patients with borderline leprosy during type 1 (reversal) reaction were selected in a non- competing retrospective cohort for three years. The nerves with treated clinically active neuropathy (Group A1) were randomized for inclusion of surgical treatment (Group A2) after one month of clinical treatment without clear signs of clinical and neurophysiological improvement. Fifteen nerves were randomly chosen for surgery while 12 were clinically treated, after steroids treatment without expected response. Nerve conduction was measured before and after treatment on four occasions. Results: The authors observed significant improvement in the following variables in the surgically treated nerves: compound motor action potential amplitude (CMAP) at elbow and above elbow and conduction velocity (CV) along the forearm. Conclusion: The improvement of CMAP amplitudes and conduction velocity (CV) along the forearm express the late effect of nerve decompression. Persistence of temporal dispersion (TD) along the elbow was related to the new reaction or to incomplete surgical solution. However, moderate reduction in CV along the elbow, without TD, was considered an indication of na expected partial remyelination. Previous gradation of the nerve lesion based on the CMAP amplitude was related to the most severe results.