Development of photoresist materials for the extreme ultraviolet lithography (EUVL) technology is one of the major challenges facing the researchers in this area. In addition to answering the well known challenges presented by the EUV radiation like the high absorption coefficients, the candidate materials should have the necessary resolution well below 100 nm feature size. We have developed an EUV interferometric lithography system for testing resists using high resolution patterns. The system is based on undulator radiation from an electron storage ring and a Lloyd mirror interferometer. We have achieved 19 nm line and space patterns (37 nm pitch) using this system. To our knowledge this is the highest resolution grating period achieved so far in any photon based lithography technique. Results showing printed grating patterns on various commercial resists are presented and practical and theoretical issues limiting the pattern quality are discussed.