Abstract: A rotary grass mower of the type having a hollow motor body and a motor mounted on top of the body having a downwardly depending shaft which carries a disc bearing grass cutter blades. A blower is provided within the body above the disc and within the body to draw air downwardly from the top of the body and then outwardly and upwardly into an annular plenum chamber which is formed in the body above the path of movement of the cutter blades. The plenum chamber provides a discharge chute for air and entrained grass cuttings and the cuttings are moved, by air from the blower, in the chute to a discharge opening thereof. The air is deflected upwardly into the plenum chamber by an upturned rim on the disc. The circulated air is used to cool the motor.