An illumination system for illuminating a reticle that moves along a scanning direction in a microlithographic projection exposure apparatus has an optical axis and an optical component producing an illumination angle distribution of the projection light. In accordance with the illumination angle distribution, a plurality of poles is illuminated in a pupil plane of the illumination system. The poles form an arrangement that is only mirror-symmetrical with respect to an axis that is orthogonal to the optical axis of the illumination, but neither parallel nor perpendicular to the scanning direction.