Temporal arteritis (Horton's disease) is a multifocal granulomatous arteritis which affects elderly people. Its prognosis depends upon the risk of blindness. In a retrospective study of 130 patients we paid special attention to the delay in diagnosis and its relation to the occurrence of ophthalmic complications. In 73 patients (56.2%), this delay exceeded 3 months and reached more than one year in 22 of them. It was not influenced by age or sex. In requests for admission, the diagnosis of temporal arteritis was suggested in only 28 of the 130 cases; 17.7% of the patients were blind. There was a significant increase in the occurrence of ophthalmic lesions when the diagnosis was delayed by 2 to 6 months. In 6 cases, blindness had been preceded by transient amaurosis. These findings confirm that temporal arteritis is belatedly diagnosed by practitioners and that blindness could be avoided by an earlier diagnosis.