THE RADIOISOTOPE RENOGRAM has been a useful adjunct to clinical practice since 1956.1At its present state of development it has two major uses: the comparison of left with right kidney function, and the comparison of left with right urinary tract excretion. It thus provides a screening technique which is useful for detecting such abnormalities as renal hypertension and ureteral obstruction. In current practice, however, the curves are not easily reproducible, and false negative and positive results are common.2Much of the difficulty stems from the continued use of techniques left over from the early developmental period when (because of partial uptake of the trace material by the liver) it was believed necessary to have the patient in the sitting position and to use small collimator apertures, short skin-crystal distances, and tilted detector tubes.3 These are precisely the qualities of instrumentation and position which magnify nonkidney