Abstract: A motor/pump (10) comprises a housing (12) defining a cavity (18) between sealed ends (14 and 16). Rotor (24) having a substantially hollow body (26) is supported by the housing (12) for rotation within the cavity (18) about a rotation axis (28) which is parallel to but offset from longitudinal axis (30) of the cavity (18). A plurality of vanes (32) are retained by the rotor (34) for movement radially of the rotation axis (28). ne vanes (32), rotor (24) and housing (12) are juxtaposed so that a substantially sealed chamber is formed between adjacent vanes (32), inner surface (34) of housing (12) and outer circumferential surface (36) of the rotor body (26). First and second ports (20, 22) are formed in the housing (12) and located so as to be disposed in different chambers.