The crystal structure of Me3SiOReO3 has been determined by single-crystal X-ray diffraction. The crystals are monoclinic, space group C2/c, with a= 11·34, b= 11·64, c= 13·44 Å, β= 99° 58′, and Z= 8. The arrangements about the silicon and rhenium atoms are tetrahedral, with mean Si–C and Re–O bond lengths of 1·92 and 1·63 Å; the Re–O–Si angle is 164 ± 5°. The experimental errors in the atomic co-ordinates of the light atoms are large because the rhenium atom dominates the X-ray scattering.