PMR and GCA are related conditions that seem to represent a continuum of disease. These conditions are relatively common and seem to be mediated by a cellular inflammatory response. Increasing evidence suggests an infectious cause (or causes) precipitating this immune response in genetically susceptible individuals. Whereas previously thought to affect primarily branch vessels of the aortic arch, GCA is now thought of as a disease in which proximal aortic involvement is frequent. Despite the potential for serious, even fatal complications, overall prognosis for patients with GCA or PMR is excellent. Corticosteroids remain the standard treatment, although not curative. Whereas the ESR is a useful indicator of disease activity, other markers which may be more precise such as creative protein and Il-6 seem to offer added information about disease activity.