A 58-year-old woman presented with the classical features of polymyalgia rheumatica. She also had a global dementia; CT scan and EEG showed diffuse cerebral disease. After steroid treatment, the polymyalgia rheumatica and dementia rapidly resolved and the CT scan and EEG became normal. The inter-relationships of the giant cell arteritides are discussed in the light of this report of the association of polymyalgia rheumatica and steroid-responsive diffuse cerebral disease.