In this paper, the subsolidus phase relations in the ternary system BaO-B2O3-TiO2 have been investigated. The phase diagram consists of 15 ternary phase regions. There exist I I binary compounds and two ternary compounds. The ternary compound, BaTi(BO3)(2), is isostructural with CaMg(CO3)(2). It crystallizes in a rhombohedral system with the space group R-3. The lattice parameters are a = 5.0205(2) and c = 16.3844(l) Angstrom. Final refinement on the diffraction data converge to R-p = 9.09, R-wp = 12.24, and R-exp = 3.75%. (C) 2003 Elsevier Science Ltd. All rights reserved.