A 72 year old woman with attacks of severe lancinating pain in the right frontotemporal region of her face had, on CT scan of the skull base, fibrous dysplasia of the right sphenoid bone, involving the areas traversed by the trigeminal nerve. Her pain ceased following treatment with methysergide. In patients with hemifacial pain but no evident facial or skull deformities, CT scan of the skull base may be helpful in elucidating the diagnosis.