In many texts on pathology and internal medicine, and even in recent publications, malignant nephrosclerosis is often regarded as the anatomical counterpart of malignant hypertension. Studying a number of such reports, we became aware that malignant nephrosclerosis cannot possibly be one single or one well-defined entity, since the descriptions of such kidneys are very much at variance, and since the various cases present somewhat different findings. As a matter of fact, changes characteristic of not only one but of several diseases may be found in some instances in one kidney. In recent years, there has been a guarded, but generally progressive, acceptance of pyelonephritis as a factor in the pathogenesis of malignant hypertension.1,2 Recently, also, emphasis has been placed on the insidious course and the high incidence of urinary tract infections.3-11 However, even in recent publications, the kidney lesions of most cases of malignant hypertension remain ascribed