Abstract: An improved Roots type supercharger for use with high performance vehicle engines. The supercharger includes rotors within a casing having rotor lobes with raised apex lands that move in a sealing relationship to the casing inside wall and rotor ends that move in a sealing relationship to the inside wall of casing end plates. A plurality of grooves are formed in at least one of the land, rotor end and end plate inside wall to reduce leakage of gases through those seals. The grooves are preferably formed generally perpendicular to the path of gas leakage through the seal.