The use of CO and O-2 chemisorption to titrate surface sites on beta-Mo2C was examined using cumene (isopropylbenzene) hydrogenation as a test reaction. The tests were carried out using beta-Mo2C samples prepared at two different temperatures so as to deposit different amounts of pyrolytic carbon on their surfaces. Synthesis at 961 K produced a surface that was substantially free of pyrolytic carbon (90% clean), while synthesis at 981 K produced a surface that was contaminated with carbon (25% clean). It was found that O-2 uptakes were about six times higher than CO uptakes, but both gave consistent turnover rates for the reaction.