The conductivity measurements on polycrystalline samples have been obtained by ac techniques and the ionic transference number has been calculated by charge/discharge d.c, technique. In the LiCr1-xAlxTiO4 (0 less than or equal to x less than or equal to 0.4) spinel systems, at low x, the solid solutions are predominantly electronic conductors but on increasing x, the level of electronic conductivity decreases giving rise to materials that are mixed conductors.