A consistent momentum interpolation approach is proposed for the discretization on collocated grids of the Eulerian-Eulerian equations governing unsteady multiphase flows. The procedure, which includes a correction for interphase forces (drag), fulfills additional requirements that a multiphase method has to meet with respect to single-phase algorithms. Results reveal that the application to multiphase flows of the simple extension of the often-used formulation for single-phase flows (Choi, 1999; Shen et al., 2001) may notably result in spurious spatial oscillations in the fields, and steady solutions of transient flows that depend significantly on the time-step size. The proposed new approach, instead, is free from these deficiencies. (C) 2013 Elsevier Ltd. All rights reserved.