The combination of a new high-resolution grating spectrometer and a spontaneous emission source has made it possible to measure precisely the 1 → 0, 2 → 1, and 2 → 0 transitions of 12C 16O relative to the accurately known 12C 16O laser lines which have been referred to pure frequency standards by Eng et al. The 1 → 0 and 2 → 0 band centers agree to within 0.0002 cm −1 with those measured relative to wavelength standards by Fourier transform spectroscopy (FTS). From a weighted simultaneous fit to the FTS-absorption, FTS-flame, our grating-emission, and microwave results, a set of calculated line positions was obtained for the 1 → 0, 2 → 1, and 2 → 0 transitions of 12C 16O. The absolute accuracy of these line positions is believed to be ±0.0005 cm −1 and we propose that the lines can be used as secondary wavenumber standards in the infrared. The spontaneous emission sequences v′ → ( v′ − 1) were measured for 12C 16O up to v′ = 20, for 13C 16O up to v′ = 11 (using a 13C-enriched sample), and for 12C 18O up to v′ = 4 (in natural abundance). Internally consistent sets of Dunham coefficients were calculated from the best available data for the molecules of 12C 16O, 13C 16O, and 12C 18O.