Alkali titanates A(2)Ti(n)O(2n+1) (A = Li, Na, K) were synthesized by hydrothermal reaction of titania powder in an aqueous alkaline solution. A nano size titania powder of 7 nm in diameter was used as the starting material to progress the hydrothermal reaction at 100degreesC. In the TiO2-LiOH-H2O system, Li2TiO3 and an amorphous phase of TiO2 were synthesized. KTiO2(OH) was synthesized as a single phase in the TiO2-KOH-H2O system at 125degreesC. Phase diagrams of the products in the TiO2-AOH-H2O (A = Li, K, Na) systems have been constructed in the region of AOH concentration from 0 to 50 mol.kg(-1)-H2O and temperature from 75 to 125degreesC.