Abstract: A method and apparatus for conditioning and monitoring a planarizing medium used for planarizing a microelectronic substrate. In one embodiment, the apparatus can include a conditioning body having a conditioning surface that engages a planarizing surface of the planarizing medium and is movable relative to the planarizing medium. A force sensor is coupled to the conditioning body to detect a frictional force imparted to the conditioning body by the planarizing medium when the conditioning body and the planarizing medium are moved relative to each other. The apparatus can further include a feedback device that controls the motion, position, or force between the conditioning body and the planarizing medium to control the conditioning of the planarizing medium.