Lithium insertion behaviour of lithium vanadate, Li1.2V3O8, was investigated using both chemical and electrochemical methods at ambient and high temperature of 100 degrees C. Additional Li+ ions up to Li4V3O8 were accommodated under 2.5 V at 100 degrees C. Each of the cell parameters changed linearly in the single-phase region of x < 2.0 in Li1+xV3O8. A constant value was observed in the two-phase region of 2.0 < x < 3.0. Further lithium insertion beyond x > 3.2 lead to an increase in cell volume of the host structure.