We calculate the rate of heating that occurs in the middle atmosphere (50--105 km) due to four exothermic reactions involving members of the odd-hydrogen family. These reactions are O+OH →O2+H, H+O2+M → HO2+M, H+O3 → OH+O2, and O+HO2 → OH+O2. The energy lost from vibrationally excited OH (produced in the third reaction) by spontaneous emission is explicitly accounted for by using detailed kinetic models, so that only a portion of the exothermicity of this reaction is converted into heat. The heating rates due to these four reactions are found to rival the oxygen-related heating rates conventionally considered in models of the middle atmosphere, e.g., those due to O+O+M →O2+M, O+O2+M → O3+M, O2+H&ngr; → O+O, and O3+h&ngr; → O+O2. The conversion of chemical potential energy into molecular translational energy (heat) by these odd-hydrogen reactions is a significant source of energy in the middle atmosphere which has not been previously considered. ¿ American Geophysical Union 1991