A projection objective for imaging a pattern arranged in an object surface of the projection objective onto an image surface of the projection objective using ultraviolet radiation has a plurality of optical elements including transparent optical elements transparent for radiation at an operating wavelength .lamda., where 260 nm>.lamda.>150 nm, an image-side pupil surface arranged between the object surface and the image surface, and an aperture-defining lens group arranged between the image-side pupil surface and the image surface for converging radiation coming from the image-side pupil surface towards the image surface to define an image-side numerical aperture NA, where 0.7.ltoreq.NA.ltoreq.1.4. The aperture-defining lens group includes at least one high-index lens made from a transparent high-index material having a refractive index n.sub.HI, where n.sub.HI>n.sub.SIO2 and where n.sub.SIO2 is the refractive index of silicon dioxide (SiO.sub.2) at the operating wavelength.