A therapeutic system comprising a therapeutic applicator for treating living tissues and an observation unit for determining the position of the applicator. The therapeutic energy applied from the applicator to the living tissues is controlled in accordance with data representing the position of the applicator, determined by the observation unit. It is therefore easy to operate the system even if the applicator and the observation unit (e.g., an MRI apparatus) are used at the same time. The image of the living tissues remains clear during the use of the therapeutic applicator.