An experimental study has been carried out for the oxidation of CO on copper chromite suppor-ted over γ-Al₂O₃ by using cycled feeds and the results were compared with those obtained by using steady noncycled feeds. When the reaction proceeds under the conditions of cyclic operation, the more strongly adsorbed oxygen is distributed more favorably over the catalytic surface and this gives rise to a substantial enhancement of the catalytic activity. Such an enhancement seems to be more distinct when the period is maintained at the level of the relaxation time of the reaction system. The effect of cyclic operation tends to becrease with the temperature because the rate of CO desorption increases with the temperature. Between the two modes of operation, Cycled and noncycled, with equal time-averaged concentration, the cycled one yields higher conversion of CO when the temperature is below 360℃, which corresponds th the desorption temperature of CO. Examined also are the effects of the period, the composition and the amplitude ratio which are considered as the major parameters in cyclic operation.