Tearing of the thoracolumbar dura mater was diagnosed after myelography in three large breed dogs. All three dogs lost the ability to walk suddenly, after a period of vigorous running or struggling. Radiographic changes suggested that the tearing of the dura was associated with intervertebral disc injury in two dogs. These dogs regained the ability to walk after medical treatment. Postmortem findings suggested that the tearing of the dura mater in the third dog was associated with nerve root injury and spinal cord haemorrhage after an episode of violent struggling.