Urea standard Kt/V(urea) (stdKt/V(urea)) has been proposed as a dose measure to assess the adequacy of dialysis treatments of arbitrary length and frequency. It is based on two fundamental assumptions: 1) that clinical outcomes for hemodialysis and peritoneal dialysis patients are equivalent and 2) that the equivalency of such clinical outcomes is achieved when the mean predialysis blood urea nitrogen or urea concentration is identical for both therapies. The relationships among urea stdKt/V(urea), equilibrated Kt/V(urea), and single-pool Kt/V(urea) are reviewed, and the assumptions required for the validity of urea stdKt/V(urea) as a universal dose measure to describe dialysis treatment adequacy are discussed. It is proposed that urea stdKt/V(urea) is a dose measure for both water-soluble and protein-bound toxin clearances; therefore, this parameter may be a practical dose measure for assessing the adequacy of dialysis during treatments of arbitrary length and frequency.