It is unclear at present which mathematical modeling Kt/V<sub>urea</sub> is valid for assessment of both long mild hemodialysis (HD) and short intensive HD, the single-pool modeling Kt/V (Kt/Vsp) based on the pre- and postdialysis serum urea concentrations, double-pool modeling Kt/V (Kt/Vdp) based on the predialysis concentration and the estimated postdialysis equilibrated concentration, or Kt/V calculated on the basis of dialyzer urea clearance, HD session duration and urea distribution volume (Kt/Vdl). Thus, the respective Kt/V during a short intensive HD was compared with its counterpart Kt/V during a long mild HD, where the same amount of urea is removed during both HD treatments. It was found that the Kt/Vsp and Kt/Vdl during short intensive HD were significantly greater than the respective Kt/V during the long mild HD. On the other hand, there was no significant difference in the Kt/Vdp between the long mild and short intensive HDs. In conclusion, Kt/Vdp may be more valid for assessment of both long mild and short intensive HDs.