The rotation-vibration spectrum of the weakly bound complex Ne-CO has been studied in the 2140 cm-1region of the fundamental stretching vibration of carbon monoxide. Spectra were obtained using two different and complementary techniques: first, a pulsed supersonic jet expansion and a tunable infrared diode laser source; and, second, a long-path, low-temperature, static gas cell and a Fourier transform infrared spectrometer. The spectrum of Ne-CO is approximately that of a T-shaped asymmetric rotor, but the complex undergoes very large amplitude intermolecular bending and stretching motions. About 106 transitions for20Ne-12C16O, and 88 for22Ne-12C16O, were assigned to the perpendicular subbands withK= 1 ← 0 and 0 ← 1 and to the parallel subband withK= 0 ← 0. Tentative observations were also made of theK= 2 ← 1 and 1 ← 2 subband centres, and of a bending combination band of the20Ne isotope. The observedB¯rotational constant in theK= 0 ground state was 0·10873 cm-1for20Ne-CO, which corresponds to an effective intermolecular separation of 3·646 Å. The observedArotational constant of about 3·57 cm-1approaches the value that would be expected in the limit of free CO internal rotation, namely 2Bfor CO or 3·84 cm-1.