The vibration-rotation spectrum of CH3I in the 2020–2440 cm-1region consists of the absorption of the perpendicular systemv2+v6(E),v5+v6(E),v3+ 2v6(E). The last two bands form a strongly coupled Fermi dyad with crossing atK′ = 4 in the (+l) stack of levels. Evidence has been found for az-axis Coriolis-type contribution to their matrix elements, linear inKand with opposite signs in the (+l) and (-l) series. Thex-yCoriolis interaction ofv2+v6(E) with all components ofv5+v6(A1+A2+E) occurs as usual in methyl halides. The spectrum does not exhibit any direct absorption to the parallel systemv5+v6(A1+A2),v3+ 2v6(A1) andv2+ 2v3(A1), whose presence is revealed by extensive perturbations of the perpendicularv5+v6,v3+ 2v6system, mostly byl(2, -1) interactions, generating anomalous rotational patterns in a wideK″ΔKrange. Accurate values of the vibration-rotation parameters of the perpendicular bands were determined by a proper use of the available data.