[en] Diagnosis, while central to scientific medicine, is nevertheless secondary to treatment, the real purpose of medical care. A brief summary of the extensive literature about the use and misuse of radiological tests is presented. Among the factors involved in the recent increases in diagnostic tests, briefly presented in this article, are the presence of the new modalities themselves, advances in understanding and treatment of diseases, an ageing population, medico-legal concerns, self referral and medical consumerism. 32 refs