The subsolidus phase relationship in the CaO-CuO-TiO2 ternary system at 950 degrees C in air was investigated. Total 26 samples having various nominal compositions were prepared by the solid-state reaction at 950 degrees C in air, and their equilibrium phases were analyzed by powder X-ray diffraction (XRD). The CaCu3Ti4O12 phase exhibits variable stoichiometry and forms as the Ca1-xCu3+xTi4O12-type (-0.019 <= x <= 0.048) solid solution at 950 degrees C in air. On the basis of our results and previous reports on the binary phase diagrams, the subsolidus phase diagram of the CaO-CuO-TiO2 ternary system could be constructed at 950 degrees C in air.