The following case is considered to be of interest; central thrombosis is rare and the radiographic appearances were most unusual. Sister A., a nun, aged 55 years. Five weeks prior to admission the first symptom was noticed, weakness of the upper eyelids, especially the right. This was followed by chest pain and pyrexia, and diplopia developed. Pleurisy was suspected, but after 5 days' rest and sedation the chest pain cleared but was followed by severe right frontal headache. The headache and diplopia had persisted. On examination the patient appeared to be of low intelligence and the following signs were detected:— In the right eye, internal strabismus, a dilated pupil not reacting to light, ptosis of the lid and some paresis of the internal rectus.