Carpal tunnel syndrome is one of the most common entrapment neuropathies of the upper limb. Electrodiagnostic studies are considered a traditional extension of the clinical neurological examination. Comparitve studies between median nerve and other unaffected nerves in the same hand improve the sensitivity of electrodiagnostic studies in diagnosis of carpal tunnel syndrome. In this work electrophysiologic tests were conducted on thirty patients symptomatic for carpal tunnel syndrome and values were matched to a control group. Our work aimed to assess the significance of the second lumbrical-interosseous distal motor latency difference test as one of the median- ulnar comparative tests and the comparison of its sensitivity with other standard electrodiagnostic tests. This book supports the value of the second lumbrical-interosseous distal motor latency difference test as a highly sensitive, quickly, easily applied technique in diagnosis of carpal tunnel syndrome