The previously reported cubic compound HgCr2O4 was prepared by thermal decomposition of Hg2CrO4 at 400 degrees C in evacuated, sealed silica tubes. Its structure was determined by a Rietveld analysis of powder diffractometer data. It is of spinel type (a = 865.8(1) pm), and it was refined to a profile residual of R-p = 0.092. The Guinier powder patterns of the isotypic yellow compounds Hg2MoO4 and Hg2WO4 were indexed with the parameters of a monoclinic C-centered lattice (Hg2MoO4 : a = 873.7(1) pm, b = 1155.1(1) pm, c = 493.17(4) pm, and beta = 115.24(1)degrees; Hg2WO4 : a = 73.4(2) pm, b = 1148.3(2) pm, c = 493.16(7) pm, and beta = 114.87(1)degrees).