The diagnostic value of excretory urography justifies its extensive use provided its limitations are recognized and its dangers are appreciated. It should not become merely a routine study, and the exposure of the patient to radiation should be limited. In a series of 21,525 intravenous urograms there have been no fatalities, but there were four serious reactions in which death was narrowly avoided. The patients were two men aged 35 and 69 years and two women aged 44 and 61 years. Three of the four required intubation and prolonged artificial respiration. Certain precautions are recommended to preclude allergies, over-sedation, and excessively rapid injections, but, in addition, it is suggested that all excretory urography be done in a surgical suite where oxygen, cut-down sets, cardiac arrest trays, and the services of an anesthetist are available.