Ruthenium-manganese bimetallic catalysts supported on alumina and silica were prepared by coimpregnation of high surface area alumina and silica with RUCl3 and MnCl2. Infrared spectroscopy was used to investigate the adsorption of CO on the system. The study revealed that the presence of Mn not only produces a low frequency band but also results in the shift of IR bands. The data has been discussed in terms of ensemble and electronic effects and the change in surface geometry produced by the addition of Mn to die catalyst system.