After reviewing the experimental data on the valence‐band offset for HgTe‐CdTe heterojunctions, we support previous suggestions of an extreme temperature dependence for this offset with a calculation based on a bond charge model. The model predicts theTdependence of the valence‐band offset to be 77% of the difference in the band‐gap temperature dependence of the heterojunction constituents. In the HgTe‐CdTe system, the opposite signs of the band gapTvariations yield an anomalously large increase in the offset of 213 meV between 0 and 300 K.