The author analyses clinical and radiological changes of the lumbar spine in patients suffering from syndrome of lumbar root compression. He describes the problem of height localisation of vertebral disc disturbances, analyses anatomical conditions of one segmental area and demonstrates his method for analysis of height localisation of disc disturbances by X-ray pictures. By comparison and studies of many X-ray pictures of the lumbar spine the author developed an easy method for localisation of the damaged disc and the narrowing of the spinal canal by precise measurements of the difference between depth (sagittal diameter) of upper and lower plate of a vertebral body. The results are based on Y-ray pictures and radiculographies of 300 patients, 156 of whom got surgical treatment. The rest was treated by conservative methods. Complete correspondence of findings by X-ray pictures and radiculographies was found in 91.4%. The surgeon found total (100%) correspondence of findings by radiculographies and intraoperative picture.