The effect of square-wave concentration-forcing operation on the rate of methanol production over two industrial catalysts was studied at 513 K and 2.86 MPa total pressure. Improvements as high as 25 percent relative to the optimal steady-state methanol production rate, in moles per gram catalyst per unit time, were obtained over BASF’s S 3-85 catalyst. This occurred in a laboratory-scale fixed-bed reactor with gas mixing for a cycling time of tau = 12 seconds and for a cycle split relative to carbon monoxide of gamma(CO) = 0.20, the rest of the cycle being hydrogen. Improvements as high as 15 percent were also obtained over Imperial Chemical Industries ICI 51-2 catalyst, in a differential plug-flow reactor for tau = 24 seconds and gamma(CO) = 0.15. These improvements were obtained for pure-component steady cycling between carbon monoxide and hydrogen with a constant carbon dioxide molar concentration of 2 per cent (BASF catalyst) or 3 percent (ICI catalyst) present in both parts of the cycle. On the other hand, no improvement over the optimal steady state was found for cycling between carbon monoxide and carbon dioxide with a constant molar concentration of 61% hydrogen nor between hydrogen and mixtures of carbon monoxide and hydrogen such as 19.6/78.4 mole percent mixture of CO/H-2.