Dialysis dose, like kidney function, is commonly expressed as a clearance scaled to some indicator of body size. With glomerular filtration rate (GFR), the traditional scaling parameter is body surface area (BSA), whereas dialysis dose, expressed as fractional clearance of urea, usually is scaled to total-body water volume, which is similar in size to the urea distribution volume, V. Results from the Hemodialysis (HEMO) Study, in which there was a possible benefit associated with a higher target Kt/V in women but not men, suggested that the concept of scaling Kt to V may not optimally account for important patient characteristics that determine the necessary dialysis dose.