A projection exposure system for microlithography includes an illuminating system (2), a reflective reticle (5) and reduction objectives (71, 72). In the reduction objective (71, 72), a first beam splitter cube (3) is provided which superposes the illuminating beam path (100) and the imaging beam path (200). In order to obtain an almost telecentric entry at the reticle, optical elements (71) are provided between beam splitter cube (3) and the reflective reticle (5). Advantageously, the reduction objective is a catadioptric objective having a beam splitter cube (3) whose fourth unused side can be used for coupling in light. The illuminating beam path (100) can also be coupled in with a non-parallel beam splitter plate. The illuminating beam path is refractively corrected in passthrough to compensate for aberrations via the special configuration of the rear side of the beam splitter plate. Advantageously, a beam splitter plate of this kind is used within a reduction objective in lieu of a deflecting mirror and only refractive components are introduced between the beam splitter plate and the reflective reticle.