Solid solutions in the system (Al-2(WO4)(3))(1-x)(Sc-2(MoO4)(3))(x) have been formed and electrically characterized. These compounds are mixed trivalent cation conducting solid electrolytes in which both Al3+ and Sc3+ cations are mobile. However, whether Al3+ or Sc3+ cations represent the main charge carrying species depends on the sample composition. In solid solutions with a low Sc-2(MoO4)(3) content (x < 0.6), the Al3+ cations are the predominant charge carriers whereas Sc3+; cations transport the main electrical current fraction in compounds with x > 0.7. In comparison to pure Al-2(WO4)(3), the electrical conductivity is maximally increased by 22 times in (Al-2(WO4)(3))(0.4)(Sc-2(MoO4)(3))(0.6), up To 7.7 X 10(-5) S cm(-1) (600 degreesC) with a corresponding activation energy of 76.0 kJ/mol. The trivalent cations are clearly identified as mobile charge carriers which generate the electrical properties within these materials. Neither conductivity contributions by oxygen anions nor by electronic species were observed.