A method and device for controlling a treatment procedure includes a treatment tool, an energy source, and a controller. The controller controls the energy source such that in a first treatment phase, power fed into the material to be treated is controlled with an increasing course. An impedance detector determines the impedance course and/or the present impedance of the material to be treated, and recognizes the achievement of an impedance minimum. A timer is started upon recognition of an impedance minimum, and upon recognition of a further impedance minimum within the specific time interval, the timer is reset. If no new impedance minimum is detected within the specific time interval and the time interval expires, the controller switches the power control to constant power or to a power course with an altered gradient. Upon fulfilling a specific criterion, there is a switchover from power control to voltage control.
