The series M1-3xLa1+x(MgW)O-6, where M = Na, K and x = 0.0, 0.11, and 0.22, was obtained by solid state reactions in air at 723 and 1273 K. The formulae were inferred from different techniques and they were in good agreement with the structure determinations. The structures could be referred to a perovskite-type and show an ordered arrangement of MgO6 and WO6 octahedra in the B-sites and also Na and La cations are ordered in layers into the A-sites. The electrical behaviour of these phases show that the activation energies are relatively high and they could be related to the previous structural analysis.