In thirty anuric patients undergoing chronic hemodialysis the KT/V values obtained with the formula: (formula; see text) were compared with the values obtained with the following two formulae: (formula; see text) The results given by formulae B and C differed from those with formula A respectively by 12.81 +/- 11.98% and 10.38 +/- 3.64%. For routine determination of KT/V we suggest the use of formulae A and C as a means of establishing rapidly, in one step, whether the hemodialytic treatment examined is adequate.