This work deals, for the first time, with the modeling of absolute line intensities in the fundamental ν 2 and ν 5 bands of CH 3 79 Br and CH 3 81 Br at 7μm. For that, four unapodized absorption spectra of CH 3 Br (natural abundance, 99% purity, P×L=0.082−0.165atm×cm, room temperature) were measured in the range 1260–1560cm −1 , at a resolution of 0.002cm −1 using a Fourier transform spectrometer Bruker IFS 120 HR. For both isotopomers, 313 line intensities were analyzed within the dyad system required to account properly for the strong Coriolis coupling between ν 2 and ν 5 . The intensity fit of experimental data led to the determination of the dipole moment derivatives d 2 =∂μ/∂q 2 and d 5 =∂μ/∂q 5 relative to the ν 2 and ν 5 bands, as well as the first-order Herman–Wallis correction in K to d 5 . The observed line intensities are fitted to 3.0% (3.3%) for ν 2 at 1309.9cm −1 and 2.6% (3.0%) for ν 5 at 1442.9cm −1 , respectively for CH 3 79 Br and CH 3 81 Br. The values derived for the vibrational band strengths of ν 2 and ν 5 are 55.7(0.6) and 39.2(0.3)cm −2 atm −1 at 296K, respectively. The corresponding assignments and line positions of the dyad from previous work [F. Kwabia Tchana, I. Kleiner, J. Orphal, N. Lacome, O. Bouba, J. Mol. Spectrosc. 228 (2004) 441] are combined with the present intensity study to provide an improved CH 3 Br database for atmospheric applications.