Wavelength measurements of 160 13C16O laser lines in the range from 1500 to 1900 cm−1 have been made with a conventional grating spectrometer. The accuracy of the measurements is about ±0.003 cm−1. Although more precise measurements of these lines will ultimately be made using microwave beating techniques, the present results should be of interest for the determination of improved molecular constants for CO and especially for the various spectroscopic applications of the CO laser.