Two recent reviews of fever of undetermined origin (FUO) in the elderly have been published.^167,168 Both point out that noninfectious inflammatory processes (i.e., rheumatic diseases) are as frequent as infections as a cause of FUO in the aged. Temporal arteritis and polymyalgia rheumatica are the two most common rheumatic conditions among the elderly. Tuberculosis was the most frequent infection in recent studies. Tumors accounted for about one eighth of cases and drug-related fever for about 6%. In some 13% of FUO cases, no diagnosis was made. Positron emission tomography in aged patients with an elevated erythrocyte sedimentation rate of unknown origin has been useful in identifying causes of inflammation. Large vessel vasculitis was most common