A truly self-consistent scheme for modelling the elastic-viscoplastic behaviour of polycrystals has, at variance with previous attempts, to preserve the elastic-viscoplastic nature of intergranular accommodation. A treatment which obeys this requirement is presented here : thanks to a tangent linearization procedure along the load path and to the use of the Laplace-Carson transform method, the problem considered is converted into a symbolically inhomogeneous elastic one with eigenstrains, which has a known classical solution.