This monograph is based on a study of 560 temporal artery biopsies carried out on patients with visual disturbances presenting to an eye clinic. Among these, 32 cases of temporal arteritis were found. In order to put this material into proper perspective, changes in temporal arteries were also studied in autopsy material. Attempts were made to relate the findings in the temporal arteries to changes in the vasculature of the retina and optic nerve. A variety of sophisticated techniques including electron microscopy of the biopsy material and trypsin digestion of available retinae for the visualization of the vasculature were used. The effort involved in this study must have been considerable but it is doubtful whether the results are commensurate with this. The conclusion that temporal artery biopsy is necessary for the firm diagnosis of temporal arteritis and for the differentiation of optic nerve involvement by other vascular processes has previously