The accurate diagnosis of lumbar radiculopathy secondary to intervertebral disc herniation or spinal stenosis remains a significant problem. Studies have stressed that misdiagnosis of root entrapment significantly contributes to the incidence of failed back syndrome. In an attempt to aid the proper selection of surgical candidates, dermatomal somatosensory evoked potentials ( DSSEP ) have been used in conjunction with standard diagnostic techniques to evaluate our patients. The advantage of this technique lies in the root specificity. The authors studied the DSSEP using two methods. In Method 1, using myelograms as the standard, the accuracy was 85.7%. In Method II, using surgical outcome as the standard, the accuracy was 87.5%. As a result, the authors have found the noninvasive, relatively inexpensive DSSEP to be a useful adjunct in the selection of patients undergoing lumbar spine surgery.