A new calcium thioborate, CaB2S4, was synthesized at high-pressure/temperature condition of 6.2 GPa and 800-1100 degreesC. The crystal structure was refined by the Rietveld method using powder X-ray diffraction data. The compound crystallizes into a cubic unit cell (a = 11.210 Angstrom, space group: M), isostructural with a high-pressure polymorph of calcium borate, CaB2O4-IV. The unit cell consists of three-dimensional linkage of BS4-tetrahedra, and calcium atoms have coordination number of 12. (C) 2002 Elsevier Science Ltd. All rights reserved.