A method of regulating an internal combustion engine, in particular involving a lean-burn mode of operation, for achieving predeterminable nitrogen oxide emission values from the internal combustion engine, wherein the .lamda.-value of a fuel-air mixture to be burnt in the internal combustion engine or an equivalent engine parameter in a defined relationship with said .lamda.-value is regulated in dependence on the amount of fuel supplied per unit of time or in dependence on the fuel energy supplied per unit of time (Q.sub.zu).