The eight possible mixed chloro-iodo and bromo-iodo complexes (including each three pairs of geometrical isomers) of osmium(IV) were separated by electrophoresis, and the detailed absorption spectra measured of acidic aqueous solutions. The bands in the near infra-red are due to intra-sub-shell transitions and the rest are electron transfer bands. The detailed assignment of symmetry types of the excited levels should be possible if both the differences of optical electronegativity, the effects of ligand-ligand repulsion, and the strong relativistic effects in bromide and iodide are taken into account. It is only possible to make definite identifications in a smaller part at present. However, the results contribute to a better understanding of the hexa-iodo complex too.