Hypertrophic olivary degeneration is usually caused by a lesion in the triangle of Guillain and Mollaret. The inciting pathology includes ischemic, inflammatory, degenerative or, less frequently, traumatic lesions. Clinically, it is usually accompanied by palatal myoclonus or other forms of segmental myoclonus. We present four patients with hypertrophic olivary degeneration studied with MRI after severe head trauma. MRI was performed between 5 and 18 months respectively after trauma. Although post-traumatic tremor was observed in three patients, none of patients showed palatal myoclonus. MRI showed multiple post-traumatic lesions within the dentato-rubro-olivary pathway associated with enlargement and increased signal intensity of the inferior olives. (J Korean Acad Rehab Med 2002; 26: 480-484)