The C and O Auger line shapes have been measured following-the room temperature adsorption of CO on a number of clean ion-bombarded transition metal surfaces, namely Ta, Nb, Ti, W, Co, Rh, Pd, Ir, and Pt. In the case of Rh, Pd, Ir, and Pt spectrum subtraction techniques had to be used to determine the C Auger line shapes due to overlap between the C and metal Auger transitions. CO decomposes on Ta, Nb, and Ti while it adsorbs molecularly on Pd, Ir, and Pt where bonding occurs via the C atom with its molecular axis normal to the surface; these differences in bonding are reflected in both C and O Auger line shapes. With Pd, Ir, and Pt the O spectra from adsorbed CO are quite different from adsorbed O 2 but resemble the O spectrum from gaseous CO thereby supporting the CO adsorption model for these metals. Some slight CO decomposition may occur with Rh whereas significant decomposition is found for Co. X-ray photoelectron spectroscopy measurements of C(1s) confirm the decomposition of CO on Co. In the case of W a mixture of CO adsorption states occurs at room temperature and appears to be reflected in the Auger spectra.