Fourier-transform interferometer and difference-frequency laser spectra of acetylene have been recorded in the 2.5- and 3.0-μm regions, yielding improved rotation-vibration constants for the ν3 fundamental and its Fermi-resonant partner, ν2 + ν4 + ν5, for their associated hot bands originating in the ν4 and ν5 bends, and for the CH stretch-bend combination bands. An analysis of the Fermi resonance gives more reliable estimates for the deperturbed constants and the anharmonic coupling. © 1990.