Abstract: Apparatus for the opto-electronic control of a flame cutting machine having photoelectric sensors of different spectral sensitivity. The sensors may be positioned within a cutting torch and directed during operation on a flame and a workpiece to be cut. The sensors are connected at their outputs with computing means to generate control signals for the advancing movement of the cutting torch relative to the workpiece. In order to reduce the impact of disturbing variables on the control signals, an electronic means for generating the quotient of the sensor output signals is connected with the outputs of at least two of said sensors. The quotient of the output magnitude of the sensors is used to control the flame cutting machine.