A retrospective analysis of clinical characteristics of 178 consecutive patients with extreme lateral lumbar disk herniation, amongst 3047 patients operated on for herniated lumbar disc, is presented. The level specific incidence of extreme lateral disc herniation (ELLDH) ranged from a low of 4.5% at L4-5 to peak of 17.4% at L3-4 although the largest number of ELLDH occurred at L4-5 and L5-S1 for a total number of 139 cases (78.1%). 43.6% of all L3 radiculopathies were caused by an L3-4 ELLDH, whereas only 4.4% of all L5 radiculopathies were caused by an L5-S1 ELLDH. Leg pain, either of the sciatic or the femoral type, was the first and dominant clinical symptom of radiculopathy, but pain radiation occurred not always in the appropriate dermatomal segment. ELLDH at upper levels (L2-3 and L3-4) caused usually none or only minor low back signs (76.2%), whereas ELLDH at lower levels more often caused moderate or major lumbar symptoms and signs (59.6%). Positive femoral nerve traction test with upper ELLDH showed a high frequency (84.4%) and reliability and is therefore an important clinical parameter in this situation. Motor deficits occurred more often (78.8%) than sensory deficits (46.6%), were usually of the monoradicular type and were therefore a more reliable clinical sign than sensory disturbances.