method) for the time discretization of an unstationary Stokes problem in D c Rd (d = 2,3) given t, f,u0; (P) find (u, p) solution to ult. = u0, ujav = 0 and: au ptAu + V p = f, divu = 0 on (0, T) x D. at Inspired by the analyses of the Backward Euler scheme performed by C. Bernardi and R. Verfiirth, we derive a posteriori estimators for the error on Vu in L2(0, T; L2(D))-norm. Our investigation is supported by numerical experiments. (C)2013 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.