Fast lithium ionic conducting glass-ceramics have been obtained by heat-treatment of glasses in the systems Li2O-M2O3-TiO2-P2O5 (M = Al and Ga). The glass-ceramics were mainly composed of LiTi2(PO4)(3) in which Ti4+ ions were partially replaced by M3+ ions. Considerable enhancement of the conductivity with the substitution of M3+ ions for Ti4+ ions was observed. The maximum conductivity obtained at room temperature was 1.3 x 10(-3) S cm(-1) for the aluminum system and 9 x 10(-4) S cm(-1) for the gallium system.