The present study deals with the estimation of deuterium recovery from the separation of water-isotopes mixture (H2O-HDO-D2O) by continuous-flow thermal diffusion. First, the equations for predicting the degrees of separation for each component in H2O-HDO-D2O system were derived by following the same procedure performed in the previous work, The recovery of deuterium (D) was then estimated from the degrees of separation of HDO and D2O and confirmed with the experimental results. (C) 2002 Elsevier Science B.V. All rights reserved.