Abstract: Methods of and apparatus for controlling a startup process of a wire insulating line until a desired outside diameter of an insulated wire is obtained. A startup control apparatus according to the invention comprises an extruder for supplying an insulating material around a core conductor, a take-up device for taking up the insulated wire, a diameter measuring device for measuring an outside diameter of the insulated wire and a processor for monitoring and controlling the line startup process. In a method of controlling the startup process of the wire insulating line, the processor calculates a target speed ratio r between the extruder and take-up device, performs a first correction in which a demanded take-up speed CA' is increased by a predetermined increment .DELTA.CA if a measured wire diameter D is equal to or greater than a target wire diameter D.sub.0, followed by a second correction in which a demanded extruder speed EX' is increased by a predetermined increment .DELTA.