The technique of perturbation chromatography using radioactive tracers has been successfully applied to chemisorption studies. Using a flow system with on-line mixing of the pure components, carrier gases of various constant compositions of CO and He, H2, and He, and CO, H2, and He were passed over a Co-Mo-Al catalyst. The steady state system was perturbed by a small sample of either C140 or tritium. The retention time of the pulse was related by chromatographic theory to the adsorption equilibrium function of CO or H2 respectively. Chemisorption isotherms were determined for CO in the 23 to 75°C range and for H2 in the 280 to 450°C range. The total pressure was slightly greater than atmospheric. Heats of adsorption were determined to be approximately 6.5 kcal/mole of CO and 18.2 kcal/mole for H2. It is proposed that the H2 adsorption is activated and follows a Langmuir dissociative mechanism. It is also proposed that the CO adsorption obeys a Freundlich relation, but at very low coverages shifts to a Langmuir two-site mechanism with apparent dissociation of the Co molecule. Some suggestions are made on the possible structure of the catalyst.