Abstract A high-resolution FT infrared spectrum of H3Si79Br (resolution 0.0022 cm−1) in the region 830-1050 cm−1 was used to analyze the fundamental bands ν2 (A1) and ν5 (E). A total of 4392 transition wavenumbers for ν2 and ν5 have been fitted, together with 632 energy values for the ν3 = 2 level, with a standard deviation of the fit of 0.123 × 10−3 cm−1. A model was used taking into account the strong Coriolis x, y resonance between ν2 and ν5, and also three local resonances: (i) an accidental Coriolis-type resonance of ν5 with 2ν3 (crossing of (kl = −13, ν5 = 1) and (K = 14, ν3 = 2) for J′ between 16 and 17); (ii) an l(±2, ∓1) resonance of the (kl = 2, ν5 = 1) and (kl = −3, ν5 = 1) levels, with a crossing for J′ between 58 and 59; and (iii) an accidental l(∓1, ±2) resonance between ν2 (K = 3) and ν5 (kl = 1, A+ and A−). Some "forbidden" transitions, due to this last resonance, were observed and included in the fit. The I-doubling constant q5 and the Coriolis resonance parameters being strongly correlated, these two resonances cannot be treated independently. Hence, q5 was fixed at zero and a value of 0.09314238(58) cm−1 was obtained for Bζ25.