A method for determining the operability of a tank-venting system on a motor vehicle subjects the signals for the volume flow through the tank-venting valve and the signals for the pressure difference between the tank interior and the ambient to a cross-covariance analysis. The above-mentioned signals are formed by a high pass in advance of forming the cross-covariance function and the maximum or the mean value of the cross-covariance function is formed with respect to the product of the two input variables. A variance measure is formed for the signal of the volume flow through the tank-venting valve and a transfer factor is computed from the variance measure and the mean value or maximum. The tank-venting system is deemed to be operational when the transfer range lies in a pregiven region. An advantage of the method is seen in the independence of the tank-pressure changes which are not caused by volume-flow changes through the tank-venting valve. Here, changes are especially of concern which are caused by the sudden generation of vapor in the tank such as caused by sloshing fuel.