This invention refers to a combine harvester which is equipped with a rotary threshing and separation unit, which consists of at least one rotor housing with sieve means (32) having sieve openings therein and a rotor element which is arranged rotatably driven inside of the rotor housing, a grain collecting element (36) which is arranged in some distance towards the sieve means, a cleaning apparatus (26) which receives the grain collected from the grain collecting element, and a sucking blower (40) which generates a sucking air flow stream.To achieve a higher fraction of chaff and broken straw to be sucked off by the sucking blower it is suggested that the air flow stream generated by the sucking blower unit is upwardly directed through a conduit (42) which guides the air flow stream from the space between the rotor housing of the rotary threshing and separation unit and the grain collecting element around a portion of the rear half of the housing of the rotary threshing and separation unit towards the sucking blower unit. According to another embodiment, besides a first discharge location for chaff and broken straw behind a first cleaning apparatus there is a second discharge location for chaff and broken straw which is sucked away from a region under the threshing and separation unit through a conduit by a sucking blower unit, and which blows a mixture of air, chaff and broken straw through a duct (70) either on the ground or into a chopper at a second discharge location
