Abstract: An annular air hammer apparatus for drilling wells has a cylindrical body which accommodates a stepped annular hammer mounted for reciprocations. A stepped air distribution tube is rigidly secured in the body and has inlet ports and exhaust ports, the tube cooperating with the hammer and defining therewith a work stroke chamber and defining a return stroke chamber with the body. A pipe for receiving drillings is stationary mounted in the air distribution tube and defines therewith a plenum. An annular member is provided between the pipe for receiving drillings and air distribution pipe, in the zone between the inlet and exhaust ports, to define an exhaust chamber between the pipe for receiving drillings and air distribution tube. The plenum and exhaust chamber permanently communicate with each other through a throttle means.