A 75-year-old woman was admitted because of fever of unknown origin (FUO). In the year before the current admission she developed myalgias and was treated for polymyalgia rheumatica with low-dose prednisone. Her complaints persisted and prednisone was discontinued. Five months before the present admission she developed fever (37.7-38.9 degrees C), malaise, fatigue and occipital headache. Laboratory tests showed an elevated erythrocyte sedimentation rate (98 mm in the first hour) and a severe hypochromic, slightly microcytic, anaemia. Although a recent temporal artery biopsy was negative, a second biopsy was taken which showed giant cell arteritis. The patient was treated with high-dose prednisone (60 mg daily) and made a full recovery. It is emphasized that temporal arteritis is a common cause of FUO in the elderly.