The polar crystal structure of diammonium [octaoxidoditellurato(IV)]tungstate, (NH(4))(2)WTe(2)O(8), was studied at high pressures using single-crystal X-ray diffraction in a diamond-anvil cell at the HASYLAB synchrotron (DESY, Hamburg, Germany). No phase transition was observed up to 7.16 GPa. However, a full structure determination at 5.09 GPa shows that the coordination number of one of the two non-equivalent Te atoms has decreased from four to three.66i79-81