Although it varies from center to center, the frequency of temporal artery biopsy in patients suspected of having temporal arteritis (TA) is relatively small. Most commonly, patients suspected of having TA are placed on prednisone for varying periods of time, and if symptoms disappear or lessen the diagnosis is made. During a recent 13-year period at Baylor University Medical Center at Dallas, 15 patients with TA had the diagnosis of TA confirmed by histological examination of a biopsy of one temporal artery. The length of the biopsied artery varied from 0.7 to 5.5 cm (mean 2.7). The 15 patients ranged in age from 68 to 94 years (mean 82, median 85), and 11 (73%) were women. In 13 of the 15 patients (87%), the lumen of the temporal artery was narrowed >95% in cross-sectional area by the panarteritis, and the temporal artery was associated with giant cells in 11 patients (73%). Large collections of erythrocytes were present in the inflamed arterial walls in 5 patients (33%). All 15 patients were treated with varying doses of prednisone with favorable response in each. Eight patients (53%) died from 1 to 105 months (mean 52, median 57) after biopsy of the temporal artery. We have neither positive nor negative evidence that the TA played a role in the patients' death. Despite the present study and numerous others in the last 70 years, the cause of TA remains a mystery.