Tomography of the kidneys is a routine procedure performed during intravenous urography. Precisely locating the kidneys, however, can be difficult. This article describes a study performed to determine a simple and accurate measurement for kidney location as a guide to obtaining initial nephrotomographic sections. The authors measured the distance from the midplane of the kidney to the posterior skin line on abdominal CT images in 26 patients. This distance averaged one-third the thickness of the abdominal region. The best depth for the nephrotomographic cut was found to be one-third the thickness of the abdomen plus the thickness of any table pad.