A lithographic projection apparatus includes an illumination system configured to provide a beam of radiation; a support configured to support a patterning device, the patterning device configured to impart the beam of radiation with a pattern in its cross section; a substrate table configured to hold a substrate, and a projection system configured to project the patterned beam of radiation onto a target portion of the substrate, wherein the illumination system has a radiation source and at least one mirror configured to enhance an output of the source. The illumination system may include a second radiation source and at least one mirror positioned between the radiation sources to image the output of the second source onto the first source, thereby enhancing the output of the source. The radiation sources may be operable to emit radiation in the EUV wavelength range.