A vibration reduction apparatus for use with a hammer tool having a hammer piston is disclosed. The hammer piston is caused to reciprocate in the cylinder by rotation of a gear wheel and crank drive. A cam is mounted around the gear wheel, a counterweight surrounds the piston cylinder, and a cam follower is provided on the counterweight. The cam follower on the counterweight is urged into contact with the cam by a biasing element. The external profile of the cam is such that rotation of the gear wheel causes oscillation of the counterweight in antiphase to motion of the hammer piston to counteract vibrations produced by operation of the hammer action of the tool. A mechanism is provided to deactivate the vibration reduction apparatus when the hammer action of the tool is deactivated.