A parameterization of the cooling rate of the earth’s middle atmosphere due to radiation transfer in the 15 μm CO2 band is proposed. The parameterization has been performed for such an atmospheric layer with local thermodynamic equilibrium (below approximately 75 km), for which in the major part of the frequency interval occupied by the 15 μm band the approximation of non-overlapping lines (above about 30 km) is justified. The overlap of lines has only been taken account of for superposed strong Q-branches at the centre of the 15 μm band. The parameterization takes into account the peculiar features of radiation transfer: 1. (1) the height step increases with the growing distance from the level, for which cooling is calculated; 2. (2) the dependence of line intensity on temperature has partially been taken account of in an explicit form. The procedure proposed is multiparametric: 42 parameters are prescribed for calculating cooling at a given level. With an error less than 0.5 K day-1 the procedure can be rec