A method for controlling the compression ratio ε in a supercharged combustion engine. The latter is provided with a control device in which a maximum final compression temperature T2,max is ascertained, and, within the framework of a precontrol, an optimum efficiency compression ratio εopt is ascertained. The knock limit is determined from the compression ratio ε, to which it corresponds, and which is ascertained from the precontrol. As a function of the efficiency curve in the characteristics map η=f, a further change occurs in compression ratio γ or a setting back of the change in compression ratio ε. The values learned for ε and the ignition angle as a function of the operating point are permanently stored in a characteristics map to which the engine control has access.