A series of Ti-substituted pyrope crystals was synthesized in the system MgO-(Na2O)-Al2O3-TiO2-SiO2-H2O at PH20 = Ptot between 25 and 30 kbars and 975 and 1000° C, using graphite heated piston-cylinder devices. The crystals, ranging up to 500 μm in diameter, were studied by X-ray, electron-microprobe and FTIR-microscope spectrometric techniques. The pyrope crystals were colourless when hem/mt or mt/wu buffers were used during the synthesis, and pale blue with the wu/iron buffer and in unbuffered runs. Sodium was not found in the synthetic crystals, titanium was always near 0.06 Ti atoms pfu, independent on the Ti-excess used in the starting material. A substitution Al2+[6]+Si4+[4]+4O2-= Ti4+[6]+□[4]+[(OH)3O^5-, providing charge balance for octahedral Ti4+-substitution is found to be compatible with all properties (number, widths, position, integrated intensity) of the stretching vibrations of defect hydroxyls, which have energies 3684, 3568, 3525 cm-1.