The electronic spectra, in the visible and u.v. regions, of HgX3–(X = Cl, Br, or I) have for the first time been obtained, by a computer technique, free from any contributions of HgX2 or HgX42–, and the resolved bands are assigned and permit identification of HgCl3– as planar with D3h symmetry, and HgI3– as pyramidal, with C3v symmetry, which suggests that the solvated species are trigonal-bipyramidal and tetrahedral, respectively; HgBr3– has possibly intermediate or pyramidal geometry.