Major improvements in energy resolution in the last two years have made the Si(Li) X-ray energy analysis system a sighificant tool for X-ray spectroscopy. Its high detection efficiency, coupled with the ability to analyse for all elements simultaneously, has led to the development of several new techniques for X-ray analysis. This article reviews the present state of the technology for this instrument with respect to performance characteristics and operating principles. A brief reference to its more important applications is als o included.