The crystal structure of the spinel polymorph of Mg2SiO4 has been refined using a single crystal synthesized at 220 kbar and 1000 ¿C. The u parameter of the structure with a=8.0649(1) ¿ is 0.3685(6). Although the refinement indicates some cation disorder in Mg2SiO4 spinel, the results are not definitive because of the similarity in the scattering factors of Mg and Si. The average Si-O and Mg-O distances are 1.655(4) and 2.070(4) ¿, respectively. The final R and RW values are 0.048 and 0.040 for 41 reflections up to sin &thgr;/λ=1.0.