This paper presents the first theoretical treatment of the electronic structure of Hg1−xMnxTe. As in the authors’ previous work on Hg1−xCdxTe, a semiempirical tight binding approach is employed, based in part on atomic energy levels, Harrison’s universal tight binding scheme, and existing experimental band structure information. The occupied Mn spin-polarized d bands are discussed and shown to have little effect on the states near the band edges. The s–p electron ‘‘complex band structure’’ of Hg1−xMnxTe is calculated in the CPA. Previous results for Hg1−xCdxTe are extended and used as a basis of comparison. The more rapid increase of the band gap with x in Hg1−xMnxTe is shown to result from the larger energy difference between cation s levels. This difference also gives rise to more pronounced disorder effects in Hg1−xMnxTe. These are discussed in the context of the CPA results for damping, band gap bowing, and the limiting electron mobilities.