On the basis of investigations involving 134 patients operated on at the National Institute of Neurosurgery, Budapest, the authors point out that herniations of the intervertebral discs at L 1/2, L 2/3, L 3/4 levels are characterized by more severe neurological changes. Paresis and autonomic disorders occur much more frequently than in lower lumbar disc herniations: paresis was found in 67 cases (50%) and bilaterally in 44 cases (32.8%), with inability to walk in 21 cases (15.7%); autonomic disturbances were noted in 36 patients (26.9%). With clear symptoms of a lumbar disc herniation a raised protein content in the CSF, more than 100 mg%, makes one suspicious of an upper lumbar lesion. In most of the cases the level of the lesion could not be exactly determined on the basis of sensory symptoms alone. The importance of myelography is stressed in determining the level. The more severe neurological changes are attributed to a medial situation of many disc hernias as found at operation, and also to unduly prolonged conservative treatment. The early postoperative results are analysed, most of which show permanent further improvement. According to our classification, the immediate postoperative results were "excellent" or "good" in 124 of the 134 patients. Except for two cases with complications, all of the patients unable to walk because of pain or paresis started to walk again after the operation. In the long-term follow-up period extending from 2 to 20 years the pain continued to improve in most of the cases, with similar, though less marked improvement in motor and autonomic disturbances. In 15 patients the condition deteriorated in the late postoperative period, but among them were 8 patients, in whom the results could be considered satisfactory as compared to the preoperative complaints. In the late postoperative period only 7 patients were unchanged or even in a worse condition than before operation.