The assignment of the wagging band, ν ₉, of methylamine was extended to weak and perturbed series in a new high-resolution spectrum in the region from 640 to 960 cm⁻¹ with extensive use of new Loomis–Wood software for Windows for the LAV molecules. Compared with previous reports, the number of assigned transitions in the wagging band (13,000) has been doubled. Most series extend as far as J = 40, even for symmetry species of lower statistical weight. For low K values (K ′ = 0 and 1), even transitions of mixed type, E₁₊₁↔E₁₋₁, have been observed. Several branches are strongly perturbed by Fermi and Coriolis-type resonances. An attempt to fit the observed transitions to a single-state model resulted in a standard deviation of 0.018 cm⁻¹.