- Original reports on temporal arteritis and polymyalgia rheumatica were reviewed before and after the introduction of steroid therapy to prevent blindness in temporal arteritis. In some cases, the original data were reworked. There is evidence that both diseases have become more benign. As a result, the perceived risk of blindness is presently overestimated, as is the perceived benefit of steroids in reducing this risk, and neither should be used as support for an essential difference between temporal arteritis and polymyalgia rheumatica. Indeed, no qualitative differences otherwise exist and both are best viewed as facets of a common disease spectrum with variable risk of adverse outcome. Some of the difficulties in dealing with diseases characterized by variable risk within present dichotomous classifications are discussed. It is likely that in many patients benign disease is presently undiagnosed. It is likely that certain classifications of temporal arteritis and polymyalgia rheumatica now in use lead to an overtreatment of some patients with relatively benign disease.