A 46-year-old female was admitted complaining of progressive, severe girdle pain consistent with the left Th3 dermatome. Neurological examination on admission revealed dysesthesia and radiating pain in the left Th3 territory. Plain X-rays and tomograms of the thoracic spine revealed a beak-like bony excrescence arising from the lamina and projecting moderately to the Th3/4 intervertebral foramen, suggesting ossification of the thoracic ligamentum flavum (OYL). Myelography showed the dural sac compressed from laterally just below the left Th3 pedicle, which suggested that the Th3 nerve root was compressed by the OYL. After Th3 nerve root decompression through hemilaminectomy and foraminotomy, the girdle pain disappeared. OYL is known to cause thoracic radiculomyelopathy, but presentation with intercostal neuralgia only is very rare. The authors review the literature and stress the importance of myelography for diagnosis.