The indications for nephrectomy in the presence of renal tuberculosis are commonly discussed. Opinion on this subject is unsettled, partly because of lack of agreement concerning the pathogenesis of the disease. One group of investigators, following Medlar's teaching, feels that renal tuberculosis always begins with bilateral involvement, while another group maintains that it begins in most cases as a unilateral infection. This argument has academic interest, but the patient desires only to be relieved of his symptoms and to have his life prolonged. Generally speaking, four clinical methods can be employed to investigate a kidney in the presence of this disease: (1) urography, (2) determination of the amount of pus present in the specimen of urine obtained by ureteral catheterization, (3) inoculation of guinea pigs with the specimen of urine obtained by ureteral catheterization, and (4) an attempt to demonstrate the bacilli of tuberculosis in stained smears of the specimen