With review of clinical chart and EMG record of 358 cases diagnosed as brachial plexus lesion in Seoul National University Hospital. We concluded as follow:

1) The sex distribution was predominently in male affection as 290 cases compared with 68 cases of female.

2) The age distribution was predominently third decades in male patient and first decade in female patient.

3) The cause of injury was traffic accident in 155 cases(43.3%), birth injury in 48 cases(13.4%), direct trauma in 46 cases(12.8%), operation complication in 24 cases(6.7%), falls in 22 cases(6.1%), idiopathic in 20 cases(5.6%), tumor in 9 cases(2.5%), others in 27 cases(7.5%).

4) The lesion site was root level in 173 cases, trunk level in 68 cases, division level in 3 cases, cord level in 30 cases, branch level in 25 cases, others in 59 cases.

5) Among 173 cases of root lesion, we compared the electrodiagnostic method with operation findings or radiologic findings such as myelograpy and computed axial tomography, and there was discrepancy between the two method in 11 cases among 39 cases comparison.

6) We grouped the cause of discrepancy into four categories. First group was overstimation of sensory nerve conduction study in 1 case. Second group was technical problem of needling of deep seated muscle in 1 case. Third group was double injury of preganglionic and postaganglionic root at the same root level in 3 cases. Forth group was complex injury of preganglionic and postganglionic root at different root or nerve level 6 cases.