Abstract: A decontaminating apparatus for removing a layer of contaminated material, such as radioactively contaminated concrete, includes two material removing devices which are driven, alternately, towards and away from one another. Each material removing device includes two rotatable scabbling drums enclosed in a shroud from which removed material is conveyed to a waste collection skip. The material removing devices are mounted at the free ends of two pivotable arms arranged to be driven in mutually opposite directions by a common drive mechanism. A frame supports the two material removing devices, the frame being connected to an articulated arm which extends from a remotely-operated vehicle. The vehicle is located on a platform which can be raised and lowered to facilitate access by the material removing devices to the entire surface under treatment.