METHODS Patients with intradural herniation of an intervertebral disc were identified and managed surgically. OBJECTIVE Illustrative cases of patients with intradural herniated discs at the mid-thoracic level are presented, the literature is reviewed, and the management of these patients is discussed. BACKGROUND Intradural herniation of an intervertebral disc is rare and most common at the lumbar level, but isolated cases have been reported at other levels. Cases reports of this entity have been published, but the surgical details have not been adequately addressed. METHODS In this report, two patients with calcified intradural herniated discs at the mid-thoracic level are presented. RESULTS Both patients had progressive paraparesis and had calcified disc material in the mid-thoracic canal. Both were treated successfully with a posterolateral extracavitary costotransversectomy and hemilaminotomy using intraoperative ultrasound and somatosensory-evoked potential monitoring. CONCLUSIONS This entity should be suspected when a calcified disc within the spinal canal is being treated. The optimal exposure is a posterolateral extracavitary costotransversectomy with a hemilaminotomy. Alternative approaches to a typical thoracic disc would be problematic in managing these patients.