X-ray lithographic systems as heretofore constructed include a low-attenuation chamber for propagating x-rays from a source toward a mask member that is positioned in close proximity to a resist-coated wafer. Both the mask and the wafer are included in the chamber which typically is either filled with helium or evacuated to a pressure less than about 10.sup.-2 Torr. In accordance with this invention, an x-ray lithographic system is constructed to enable establishment in the wafer-to-mask region of a controlled atmosphere that is separate and distinct from that maintained in the low-attenuation chamber. In this way, an improved lithographic system with advantageous throughput and other characteristics is realized.