Painful symptomatology in the lower limbs coming on with walking must not systematically be attributed to arteritis of the lower limbs. Among the characteristics which may suggest that this "claudication" is due to a narrowed lumbar canal, is the presence of paresthesia and above all the clear improvement when the patient is seated or adopts a lumbar kyphotic position. It is therefore extremely important to keep in mind the radicular topography of pain and neurological deficit. The congenitally narrow lumbar canals rarely produce problems unless there is further narrowing of the lumbar or radicular canal by a disco-osteophytic projection anteriorly, a posterior articular osteophytic projection posteriorly, thickening of the ligamentum flavum, an abnormal widening of the dural sheath, or excess peridural fat. Among the complementary investigations, CAT scan is useful to analyse the structures involved, but this examination is carried out in decubitus, i.e., without lordosis, while narrowing principally appears on lumbar extension, i.e., in the upright position. Saccoradiculography therefore remains the investigation of choice, performed in the seated and upright position. It can objectively assess the degree of narrowing and analyse the proportion due to the anterior discal or posterior articular component. This investigation should only be requested after failure of medical treatment based above all on analgesics, physiotherapy in lumbar kyphosis, and an abdomino-lumbar corset support. In the event of failure of medical treatment and if the patient is very handicapped, one most often resorts to decompressive surgery, however when narrowing is principally due to a discal projection, one may attempt discolysis with chymopapain.