Infrared laser absorption spectroscopy in conjunction with a cold molecular beam of W(CO)6 has yielded the rotationally resolved spectrum of this spherical top molecule near 2000 cm-1. Octahedral splitting has been resolved for the first time and is analyzed using the highly spherical top data system (hTDS) developed at Dijon. In addition, a perpendicular band of the symmetric top molecule W(12C 16O)513C 16O was observed in natural abundance. The spectroscopic parameters derived for this molecule, together with electron-diffraction data, provided a value for B0 of the dominant isotopomer, and a check on the consistency of the analysis of the spectra. © 2000 American Institute of Physics.