Ossification of the ligamentum flavum (OLF) has been recognised as a definite clinical entity as an ossification of the posterior longitudinal ligament. It has been known that the incidence of OLF is high in Japan and OLF usually occurs in the thoracic and lumbar region. Recently OLF has received considerable attention as a cause of myelopathy. OLF is quite distinct from “hypertrophy” of the ligamentum flvum. We experienced 2 cases of OLF with neurological symptom, which were treated by decompressive laminectomy and removal of the ossified ligamentum flavum. So remarkable symptomatic improvement was obtained.