Abstract: A gerotor pump comprises a rotor chamber having a longitudinally extending central axis, an outer rotor rotatable in the rotor chamber with a radial clearance between an outer periphery of the outer rotor and the rotor chamber, an inner rotor rotatable in the outer rotor and cooperably engageable therewith to define a plurality of pumping chambers having respective volumes that vary when, in use, the inner rotor rotates relative to the outer rotor. The inner rotor is rotatable about an axis of rotation spaced from the central axis and contained in a first plane that contains the central axis and the rotor chamber is configured such that the radial clearance in at least one direction in the first plane is greater than at least one radial clearance in a second plane that extends perpendicular to the first plane and contains the central axis.