Two patients who developed intraspinal hematomas associated with anticoagulation therapy are described, and the pathology, clinical presentation, risks, evaluation and management of this rare hemorrhagic consequence, which results in spinal cord injury (SCI), are discussed. A 49-year-old man was taking warfarin sodium 7.5 mg orally every day for two weeks for thrombophlebitis. Prothrombin time (PT) was 24 sec (control = 17 sec). Two days after a dosage reduction for a PT of 36.5 sec (control = 11 sec), he developed severe neck pain, numbness and weakness of the legs, and then quadriplegia. Warfarin therapy was discontinued, and 25 mg of phytonadione was administered intravenously. An epidural hematoma was removed via a C3-C6 laminectomy, and the patient remains a C3 complete quadriplegic. The second patient was a 64-year-old man who was taking warfarin sodium 5 mg and 7.5 mg orally on alternate days following an aortic-valve replacement. PT was maintained at 1.5 times the control value. Four years later, he fell and sustained flexion distraction and compression injuries of the spine at the L1-L2 level. He complained of severe neck pain and headache. Warfarin therapy was stopped, and 10 mg of phytonadione was administered i.v. During a hospital transfer he developed complete paraplegia. PT was 12.4 sec (control = 10.8 sec). Twelve days later, a laminectomy was performed to remove the T6-L1 subdural hematoma revealed by computed tomography (CT). The patient remains a T5 complete paraplegic. Unlike intracranial hemorrhage, intraspinal hemorrhage usually occurs in the epidural space, most often in the dorsal thoracic spine.(ABSTRACT TRUNCATED AT 250 WORDS)