Full structural studies of condensed media under high pressure by neutron powder diffraction have been limited in practice to 2–3 GPa for several decades. This range is in general too small to allow a precise determination of the pressure dependence of atomic coordinates. As a consequence, almost no direct measurements exist, for example, of the pressure dependence of the bond lengths in H2and the planetary ices. In this letter, a technique is presented which makes it possible to pressurize samples of 35 mm3volume up to 30 GPa and to collect neutron diffraction patterns in a few hours by time‐of‐flight techniques. This method provides data which can be treated by Rietveld profile refinement methods, as demonstrated on a sample of D2O ice VII at 26 GPa. This represents a tenfold increase of the pressure range over which refinable neutron diffraction data can be obtained and should have a number of applications in such fields as fundamental physicochemistry, and geo‐ and planetary sciences. ©1995 American Institute of Physics.